79 results on '"Christopher N. Johnson"'
Search Results
2. Cats are a key threatening factor to the survival of local populations of native small mammals in Australia’s tropical savannas: evidence from translocation trials with
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Ethan Page, Ian J. Radford, Iain J. Gordon, Katherine Tuft, John C. Z. Woinarski, Michael J. Lawes, Anke S. K. Frank, Alaric Fisher, Sarah Legge, Tegan May, Alex James, and Christopher N. Johnson
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0106 biological sciences ,Extinction ,CATS ,Ecology ,animal diseases ,Biodiversity ,Context (language use) ,Management, Monitoring, Policy and Law ,Biology ,010603 evolutionary biology ,01 natural sciences ,Predation ,010601 ecology ,Threatened species ,Feral cat ,Mammal ,Ecology, Evolution, Behavior and Systematics - Abstract
Context Invasive predators are a key threat to biodiversity worldwide. In Australia, feral cats are likely to be responsible for many extinctions of native mammal species in the south and centre of the continent. Aims Here we examine the effect of feral cats on native rodent populations in the second of two translocation experiments. Methods In a wild-to-wild translocation, we introduced pale field rats, Rattus tunneyi, whose populations are declining in the wild, into two pairs of enclosures where accessibility by feral cats was manipulated. Key results Individual rats translocated into enclosures accessible to cats were rapidly extirpated after cats were first detected visiting the enclosures. Rats in the enclosure not exposed to cats were 6.2 times more likely to survive than those exposed to cats. Two individual cats were responsible for the deaths of all but 1 of 18 cat-accessible rats. Rats in the site with denser ground cover persisted better than in the site with more open cover. Conclusions These results are consistent with our previous study of a different native rat species in the same experimental setup, and provide further evidence that, even at low densities, feral cats can drive local populations of small mammals to extinction. Implications Effective feral cat control may be necessary to enable recovery of small mammals.
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- 2021
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3. Structure-Based Design of Potent and Orally Active Isoindolinone Inhibitors of MDM2-p53 Protein–Protein Interaction
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Benoit Carbain, Keisha Hearn, Ildiko Maria Buck, Burcu Anil, Sarah J. Cully, Gianni Chessari, Jane A. Endicott, John Lunec, Neil T. Thompson, Juan Castro, Roger J. Griffin, Rhian S. Holvey, Karen Haggerty, Charlotte H. Revill, Ruth H. Bawn, Stephen R. Wedge, Christiane Riedinger, Christopher N. Johnson, Bernard T. Golding, Lynsey Fazal, Ian R. Hardcastle, Mladen Vinkovic, Claire E. Jennings, Jong Sook Ahn, Bian Zhang, Pamela A. Williams, Celine Cano, Suzannah J. Harnor, Ben Cons, Stephen J. Hobson, E. Anscombe, Jeffrey D. St. Denis, Steven Howard, David R. Newell, Emiliano Tamanini, Nicola E. Wilsher, Miller Duncan Charles, Huw D. Thomas, Timothy J. Blackburn, Martin E.M. Noble, Judith Reeks, Yan Zhao, and Luke Bevan
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Male ,Metabolite ,Mice, Nude ,Antineoplastic Agents ,Bone Neoplasms ,Isoindoles ,Pharmacology ,Crystallography, X-Ray ,01 natural sciences ,Structure-Activity Relationship ,03 medical and health sciences ,chemistry.chemical_compound ,Drug Stability ,In vivo ,Cell Line, Tumor ,Drug Discovery ,Animals ,Humans ,Structure–activity relationship ,neoplasms ,Cell Proliferation ,030304 developmental biology ,Mice, Inbred BALB C ,Osteosarcoma ,0303 health sciences ,Molecular Structure ,biology ,Chemistry ,Proto-Oncogene Proteins c-mdm2 ,Ligand (biochemistry) ,Xenograft Model Antitumor Assays ,Cytostasis ,Small molecule ,In vitro ,0104 chemical sciences ,Macaca fascicularis ,010404 medicinal & biomolecular chemistry ,Microsomes, Liver ,biology.protein ,Molecular Medicine ,Mdm2 ,Female ,Protein Multimerization ,Tumor Suppressor Protein p53 ,Protein Binding - Abstract
Inhibition of murine double minute 2 (MDM2)-p53 protein-protein interaction with small molecules has been shown to reactivate p53 and inhibit tumor growth. Here, we describe rational, structure-guided, design of novel isoindolinone-based MDM2 inhibitors. MDM2 X-ray crystallography, quantum mechanics ligand-based design, and metabolite identification all contributed toward the discovery of potent in vitro and in vivo inhibitors of the MDM2-p53 interaction with representative compounds inducing cytostasis in an SJSA-1 osteosarcoma xenograft model following once-daily oral administration.
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- 2021
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4. Effectiveness of thermal cameras compared to spotlights for counts of arid zone mammals across a range of ambient temperatures
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Hugh W. McGregor, Katherine E. Moseby, Christopher N. Johnson, and Sarah Legge
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0106 biological sciences ,Distance sampling ,Range (biology) ,Spotlighting ,Nocturnal ,Biology ,010603 evolutionary biology ,01 natural sciences ,010601 ecology ,Environmental temperature ,Thermal ,Animal Science and Zoology ,Transect ,Ecology, Evolution, Behavior and Systematics ,Arid zone ,Remote sensing - Abstract
Effective monitoring of mammal species is critical to their management. Thermal cameras may enable more accurate detection of nocturnal mammals than visual observation with the aid of spotlights. We aimed to measure improvements in detection provided by thermal cameras, and to determine how these improvements depended on ambient temperatures and mammal species. We monitored small to medium sized mammals in central Australia, including small rodents, bettongs, bilbies, European rabbits, and feral cats. We conducted 20 vehicle-based camera transects using both a spotlight and thermal camera under ambient temperatures ranging from 10°C to 35°C. Thermal cameras resulted in more detections of small rodents and medium sized mammals. There was no increased benefit for feral cats, likely due to their prominent eyeshine. We found a strong relationship between increased detections using thermal cameras and environmental temperature: thermal cameras detected 30% more animals than conventional spotlighting at approximately 15°C, but produced few additional detections above 30°C. Spotlighting may be more versatile as it can be used in a greater range of ambient temperatures, but thermal cameras are more accurate than visual surveys at low temperatures, and can be used to benchmark spotlight surveys.
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- 2021
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5. Accidents alter animal fitness landscapes
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Christopher N. Johnson, Barry W. Brook, Rory P. Wilson, Jessie C. Buettel, and Rebecca Wheatley
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0106 biological sciences ,Fitness landscape ,Ecology ,Movement ,010604 marine biology & hydrobiology ,Energy (esotericism) ,Accident risk ,Affect (psychology) ,010603 evolutionary biology ,01 natural sciences ,Predation ,Habitat ,Accidents ,Predatory Behavior ,Animals ,Biological dispersal ,Psychology ,Environmental planning ,Ecosystem ,Ecology, Evolution, Behavior and Systematics - Abstract
Animals alter their habitat use in response to the energetic demands of movement ('energy landscapes') and the risk of predation ('the landscape of fear'). Recent research suggests that animals also select habitats and move in ways that minimise their chance of temporarily losing control of movement and thereby suffering slips, falls, collisions or other accidents, particularly when the consequences are likely to be severe (resulting in injury or death). We propose that animals respond to the costs of an 'accident landscape' in conjunction with predation risk and energetic costs when deciding when, where, and how to move in their daily lives. We develop a novel theoretical framework describing how features of physical landscapes interact with animal size, morphology, and behaviour to affect the risk and severity of accidents, and predict how accident risk might interact with predation risk and energetic costs to dictate movement decisions across the physical landscape. Future research should focus on testing the hypotheses presented here for different real-world systems to gain insight into the relative importance of theorised effects in the field.
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- 2021
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6. Space use and temporal partitioning of sympatric Tasmanian devils and spotted‐tailed quolls
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Georgina E. Andersen, Christopher N. Johnson, and Menna E. Jones
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0106 biological sciences ,Dasyurus maculatus ,education.field_of_study ,Ecology ,010604 marine biology & hydrobiology ,Home range ,Population ,Devil facial tumour disease ,Biology ,biology.organism_classification ,medicine.disease ,010603 evolutionary biology ,01 natural sciences ,Predation ,Sarcophilus ,medicine ,Quoll ,education ,Ecology, Evolution, Behavior and Systematics ,Marsupial - Abstract
Sympatric species can minimise interspecific competition by spatial avoidance or by altering their temporal activity to reduce encounter rates. The Tasmanian devil (Sarcophilus harrisii), the largest carnivorous marsupial, coexists with the smaller spotted‐tailed quoll (Dasyurus maculatus) in Tasmania, Australia. Quolls may be susceptible to interspecific competition from devils, because they utilise similar habitats, consume similar prey species and are displaced by devils at food sources. Such competition might cause quolls to spatially or temporally avoid devils. To investigate whether spatial or temporal avoidance occurred, we deployed GPS collars on sympatric devils and quolls and conducted a camera survey at a site in northwest Tasmania where the devil population was not affected by devil facial tumour disease. GPS tracking coincided with the lactation period when devils and quolls had young in dens and continued until weaning occurred. We found little spatial segregation of home range and core area placement between devils and quolls and among devils. Quolls showed more spatial segregation within the sexes than between them. Devils had larger home ranges than quolls. Male devils had larger home ranges than females, but there was no difference in home range size between the sexes of quolls. Females of both species travelled significantly further per night than did males. There was moderate temporal partitioning between the two species: devil activity peaked after dusk and devils remained active until the early morning, while quoll activity showed distinct peaks around dusk and dawn. In conclusion, quolls did not spatially avoid devils but moderate temporal partitioning occurred. It is plausible that quolls are active at different times of the diel cycle to reduce encountering devils, but further studies are needed to resolve the cause of this temporal partitioning.
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- 2020
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7. Short-term pain before long-term gain? Suppression of invasive primary prey temporarily increases predation on native lizards
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Hannah B. Cliff, Richard Heyward, Grant Norbury, Menna E. Jones, Christopher N. Johnson, and Roger P. Pech
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2. Zero hunger ,0106 biological sciences ,Ecology ,Community ,biology ,Numerical response ,Lizard ,010604 marine biology & hydrobiology ,Functional response ,Zoology ,15. Life on land ,010603 evolutionary biology ,01 natural sciences ,Invasive species ,Predation ,Abundance (ecology) ,biology.animal ,Prey switching ,Ecology, Evolution, Behavior and Systematics - Abstract
The control of invasive species can have cascading and at times undesirable effects on the wider ecological community. Effective management requires that the ecosystem-wide effects of removing invasive species be understood. We investigated the effects of large-scale rabbit control on the abundance (numerical response) and diet (functional response) of an invasive predator (ferret, Mustela putorius furo) that preys on rabbits (Oryctolagus cuniculus), as well as the subsequent predation pressure experienced by alternative prey species (total response), in New Zealand’s dryland habitats. Following rabbit control, ferret densities declined but surviving ferrets increased their per capita consumption of lizards and invertebrates, two key native prey groups. Rabbit control increased predation pressure on lizards, but reduced it on invertebrates. While rabbit control can negatively impact some groups of alternative prey up to 18 months post-control, it probably benefits them in the longer term because prey-switching by ferrets tended to reduce with time, and regeneration of vegetation previously over-grazed by rabbits is likely to reduce exposure of native prey to predation. While confirming these benefits will require longer-term monitoring, our results support management actions that limit short-term fluctuations in rabbit abundance and maintain them at low abundance.
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- 2020
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8. Sahul's megafauna were vulnerable to plant-community changes due to their position in the trophic network
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John Llewelyn, Frédérik Saltré, Sara N. de Visser, Daniel B. Stouffer, Matthew C. McDowell, Katharina J. Peters, Giovanni Strona, Christopher N. Johnson, Corey J. A. Bradshaw, Ecological Data Science, Organismal and Evolutionary Biology Research Programme, Olff group, University of Zurich, and Llewelyn, John
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10207 Department of Anthropology ,0106 biological sciences ,AUSTRALIA ,Environmental change ,Pleistocene ,Evolution ,010603 evolutionary biology ,01 natural sciences ,Predation ,FOOD WEBS ,03 medical and health sciences ,Behavior and Systematics ,Late Pleistocene ,biology.animal ,Megafauna ,Trophic cascade ,ecological network ,Ecology, Evolution, Behavior and Systematics ,Trophic level ,030304 developmental biology ,BODY-SIZE ,LATE QUATERNARY MEGAFAUNA ,0303 health sciences ,Ecology ,biology ,food web ,300 Social sciences, sociology & anthropology ,Vertebrate ,BIOTIC INTERACTIONS ,Plant community ,social sciences ,15. Life on land ,musculoskeletal system ,EXTINCTION RISK ,MAMMAL FAUNAS ,humanities ,PLEISTOCENE CLIMATE-CHANGE ,1105 Ecology, Evolution, Behavior and Systematics ,Geography ,1181 Ecology, evolutionary biology ,coextinction ,extinction event ,TOP-DOWN ,geographic locations ,NARACOORTE CAVES - Abstract
Extinctions stemming from environmental change often trigger trophic cascades and coextinctions. Bottom-up cascades occur when changes in the primary producers in a network elicit flow-on effects to higher trophic levels. However, it remains unclear what determines a species' vulnerability to bottom-up cascades and whether such cascades were a large contributor to the megafauna extinctions that swept across several continents in the Late Pleistocene. The pathways to megafauna extinctions are particularly unclear for Sahul (landmass comprising Australia and New Guinea), where extinctions happened earlier than on other continents. We investigated the potential role of bottom-up trophic cascades in the megafauna extinctions in Late Pleistocene Sahul by first developing synthetic networks that varied in topology to identify how network position (trophic level, diet breadth, basal connections) influences vulnerability to bottom-up cascades. We then constructed pre-extinction (-80 ka) network models of the ecological community of Naracoorte, south-eastern Sahul, to assess whether the observed megafauna extinctions could be explained by bottom-up cascades. Synthetic networks showed that node vulnerability to bottom-up cascades decreased with increasing trophic level, diet breadth and basal connections. Extinct species in the Naracoorte community were more vulnerable overall to these cascades than were species that survived. The position of extinct species in the network - tending to be of low trophic level and therefore having relatively narrow diet breadths and fewer connections to plants - made them vulnerable. However, these species also tended to have few or no predators, a network-position attribute that suggests they might have been particularly vulnerable to new predators. Together, these results suggest that trophic cascades and naivety to predators could have contributed to the megafauna extinction event in Sahul.
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- 2022
9. Long-Distance Movements of Feral Cats in Semi-Arid South Australia and Implications for Conservation Management
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Jeroen Jansen, David Peacock, Robert Brandle, Christopher N. Johnson, Katherine E. Moseby, Hugh W. McGregor, Menna E. Jones, Geoff Axford, Sebastien Comte, and Abbey T. Dean
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0106 biological sciences ,invasive species management ,Range (biology) ,space use ,Home range ,Veterinary medicine ,home range ,010603 evolutionary biology ,01 natural sciences ,Article ,relocation ,SF600-1100 ,Felis catus ,reinvasion ,CATS ,General Veterinary ,National park ,telemetry ,Space use ,15. Life on land ,landscape ,Arid ,introduced predator ,010601 ecology ,Fishery ,Geography ,QL1-991 ,Feral cat ,Animal Science and Zoology ,Relocation ,Zoology - Abstract
Movements that extend beyond the usual space use of an animal have been documented in a range of species and are particularly prevalent in arid areas. We present long-distance movement data on five feral cats (Felis catus) GPS/VHF-collared during two different research projects in arid and semi-arid Australia. We compare these movements with data from other feral cat studies. Over a study period of three months in the Ikara-Flinders Ranges National Park, 4 out of 19 collared cats moved to sites that were 31, 41, 53 and 86 km away. Three of the cats were males, one female, their weight was between 2.1 and 4.1 kg. Two of the cats returned to the area of capture after three and six weeks. During the other study at Arid Recovery, one collared male cat (2.5 kg) was relocated after two years at a distance of 369 km from the area of collar deployment to the relocation area. The movements occurred following three years of record low rainfall. Our results build on the knowledge base of long-distance movements of feral cats reported at arid study sites and support the assertion that landscape-scale cat control programs in arid and semi-arid areas need to be of a sufficiently large scale to avoid rapid reinvasion and to effectively reduce cat density. Locally, cat control strategies need to be adjusted to improve coverage of areas highly used by cats to increase the efficiency of control operations.
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- 2021
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10. The short-term response of feral cats to rabbit population decline: Are alternative native prey more at risk?
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Katherine E. Moseby, Hugh W. McGregor, Christopher N. Johnson, and Sarah Legge
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0106 biological sciences ,education.field_of_study ,CATS ,Ecology ,animal diseases ,010604 marine biology & hydrobiology ,Population ,Wildlife ,Zoology ,Introduced species ,Biology ,010603 evolutionary biology ,01 natural sciences ,Predation ,Population decline ,Mesopredator release hypothesis ,Prey switching ,education ,Ecology, Evolution, Behavior and Systematics - Abstract
The impacts of invasive predators can be amplified by high densities of invasive prey species. In Australia, hyper abundant rabbit populations lead to high densities of feral cats and correspondingly high impact of cats on native species, especially small mammals. Therefore, it would be expected reducing rabbits could also reduce abundance of cats, and thereby alleviate predation on native small mammals. However, cats might respond to the loss of rabbits by prey-switching to native small mammals, resulting in increased predation on those species. Our aim was to understand the short-term effects of an experimental reduction of rabbit abundance on feral cats and their small-mammal prey in arid South Australia. We reduced the rabbit population in a 37 km2 experimental enclosure by ~ 80%, while monitoring an adjacent unmanipulated area as a control. Cat activity and survival of VHF-collared cats in the enclosure decreased by 40% following the rabbit reduction. Surviving cats increased their consumption of reptiles, birds and invertebrates, but they nevertheless evinced hunger by increased intake of experimentally-supplied sausages. There was no change in either the proportion of cat scats that contained remains of small mammals, or the rate at which video-collared cats were recorded killing small mammals, even though the activity of small mammals declined. Our results demonstrate that individual feral cats prey-switch in response to removal of their primary prey. However, we also show that survival and overall activity of cats decreased, which could result in net, long-term benefits for native prey threatened by cats. Management of feral cats using food lures or baits would also be more effective when introduced prey are scarce, as cats are more likely to eat novel food.
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- 2019
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11. Home range size scales to habitat amount and increasing fragmentation in a mobile woodland specialist
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Sebastien Comte, Menna E. Jones, Christopher N. Johnson, Kirstin M. Proft, and Riana Gardiner
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0106 biological sciences ,restoration ,Range (biology) ,Home range ,home range ,Woodland ,010603 evolutionary biology ,01 natural sciences ,03 medical and health sciences ,lcsh:QH540-549.5 ,fragmentation ,Ecology, Evolution, Behavior and Systematics ,030304 developmental biology ,Nature and Landscape Conservation ,Original Research ,0303 health sciences ,Habitat fragmentation ,Ecology ,biology ,habitat amount ,fungi ,Fragmentation (computing) ,Bettong ,15. Life on land ,biology.organism_classification ,Geography ,Habitat ,lcsh:Ecology ,Species richness ,management - Abstract
Studies of impacts of fragmentation have focused heavily on measures of species presence or absence in fragments, or species richness in relation to fragmentation, but have often not considered the effects of fragmentation on ranging behavior of individual species. Effective management will benefit from knowledge of the effects of fragmentation on space use by species.We investigated how a woodland specialist, the eastern bettong (Bettongia gaimardi), responded to fragmentation in an agricultural landscape, the Midlands region of Tasmania, Australia. We tested whether individual bettongs could adjust home range size to maintain access to essential habitat across three sites differing in degree of fragmentation.We used GPS tracking to measure the home ranges of individual bettongs. Our models tested the effects of habitat aggregation and habitat amount measured at two radii comparable to a typical core range (250 m) and a typical home range (750 m), and habitat quality and sex on individual home range. We also tested the relationship between fragmentation on woodland used to determine whether individuals could compensate for fragmentation.Depending on the spatial scale of fragmentation measured, bettongs altered their movement to meet their habitat requirements. Our top model suggested that at the core range scale, individuals had smaller ranges when habitat is more aggregated. The second model showed support for habitat amount at the core range, suggesting individuals can occupy larger areas when there is a higher amount of habitat, regardless of configuration.Species that are relatively mobile may be able to compensate for the effects of habitat fragmentation by altering their movement. We highlight that any patch size is of value within a home range and management efforts should focus on maintaining sufficient habitat especially at the core range scale., For a mobile species that can cross gaps, the configuration of patches does not hinder movement given there is sufficient habitat.
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- 2019
12. Temporal partitioning of activity: rising and falling top‐predator abundance triggers community‐wide shifts in diel activity
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Calum X. Cunningham, Leon A. Barmuta, Menna E. Jones, Vince Scoleri, and Christopher N. Johnson
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0106 biological sciences ,Ecological niche ,Ecology ,010604 marine biology & hydrobiology ,media_common.quotation_subject ,Niche differentiation ,Biology ,010603 evolutionary biology ,01 natural sciences ,Competition (biology) ,Intraspecific competition ,Predation ,Mesopredator release hypothesis ,Trophic cascade ,Ecology, Evolution, Behavior and Systematics ,media_common ,Apex predator - Abstract
Top predators cause avoidance behaviours in competitors and prey, which can lead to niche partitioning and facilitate coexistence. We investigate changes in partitioning of the temporal niche in a mammalian community in response to both the rapid decline in abundance of a top predator and its rapid increase, produced by two concurrent natural experiments: 1) the severe decline of the Tasmanian devil due to a transmissible cancer, and 2) the introduction of Tasmanian devils to an island, with subsequent population increase. We focus on devils, two mesopredators and three prey species, allowing us to examine niche partitioning in the context of intra- and inter-specific competition, and predator-prey interactions. The most consistent shift in temporal activity occurred in devils themselves, which were active earlier in the night at high densities, presumably because of heightened intraspecific competition. When devils were rare, their closest competitor, the spotted-tailed quoll, increased activity in the early part of the night, resulting in increased overlap with the devil's temporal niche and suggesting release from interference competition. The invasive feral cat, another mesopredator, did not shift its temporal activity in response to either decreasing or increasing devil densities. Shifts in temporal activity of the major prey species of devils were stronger in response to rising than to falling devil densities. We infer that the costs associated with not avoiding predators when their density is rising (i.e. death) are higher than the costs of continuing to adopt avoidance behaviours as predator densities fall (i.e. loss of foraging opportunity), so rising predator densities may trigger more rapid shifts. The rapid changes in devil abundance provide a unique framework to test how the non-lethal effects of top predators affect community-wide partitioning of temporal niches, revealing that this top predator has an important but varied influence on the diel activity of other species.
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- 2019
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13. Trophic rewilding establishes a landscape of fear: Tasmanian devil introduction increases risk‐sensitive foraging in a key prey species
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Menna E. Jones, Kaely Kreger, Christopher N. Johnson, Calum X. Cunningham, and Tracey Hollings
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0106 biological sciences ,biology ,Ecology ,010604 marine biology & hydrobiology ,Foraging ,biology.organism_classification ,010603 evolutionary biology ,01 natural sciences ,Predation ,Sarcophilus ,Geography ,Tasmanian devil ,Brushtail possum ,Quoll ,Trophic cascade ,Ecology, Evolution, Behavior and Systematics ,Apex predator - Abstract
Global declines of large carnivores have reduced the 'landscape of fear' that constrains the behaviour of other species. In recent years, active and passive trophic rewilding have potentially begun restoring these lost top-down controls. The Tasmanian devil Sarcophilus harrisii has declined severely due to a novel transmissible cancer. In response to extinction fears, devils were introduced to the devil-free Maria Island, where their abundance rapidly increased. We tested how this introduction influenced risk-sensitive foraging in the common brushtail possum Trichosurus vulpecula, a major prey species for devils, using giving-up densities (GUDs). Before the introduction of devils, possum GUDs on Maria Island were indistinguishable from the long-diseased region of Tasmania, where devils have been rare since ∼2000. Three years after devil introduction, GUDs were 64% higher on Maria Island than the control region, demonstrating that after an initial period of high mortality, possums quickly adopted risk-sensitive foraging behaviours. Devil activity across Maria Island was variable, leading to a heterogeneous landscape of fear and highlighting that top predators must be at functional densities to elicit behavioural responses from prey. Our study provides strong evidence that top predators modify the behaviour of prey by instilling fear, causing rapid ecological change following recoveries.
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- 2019
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14. Chronic stress in superb fairy‐wrens occupying remnant woodlands: Are noisy miners to blame?
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Christopher N. Johnson, Menna E. Jones, and Glen C. Bain
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0106 biological sciences ,Habitat fragmentation ,Ecology ,biology ,010604 marine biology & hydrobiology ,Noisy miner ,Interspecific competition ,Woodland ,15. Life on land ,biology.organism_classification ,010603 evolutionary biology ,01 natural sciences ,Passerine ,biology.animal ,Manorina ,Malurus ,Haemoproteus ,Ecology, Evolution, Behavior and Systematics - Abstract
Interactions between competing species may be intensified when they are restricted to small patches of remnant habitat, potentially increasing physiological stress in individuals. The effects of interspecific competition on stress in wildlife remain largely unexplored. In Australia, remnant woodlands are often dominated by aggressive honeyeaters, especially the noisy miner (Manorina melanocephala). Harassment of smaller birds by miners may result in their exclusion from suitable woodland habitat. We tested whether the presence of noisy miners is also associated with elevated stress in a model species of small passerine bird, the superb fairy‐wren (Malurus cyaneus). We sampled wrens from six sites, three remnant woodlands with noisy miners and three larger fragments of reserved habitat without noisy miners. Differential white blood cell counts were used to infer levels of chronic stress. We also assessed variation in body condition and the prevalence of blood parasites (Haemoproteus spp.) to test for associations between stress and parasitemia. The mean heterophil‐to‐lymphocyte (H:L) ratio was 1.8 × higher among superb fairy‐wrens living in miner‐dominated woodlands, suggesting higher levels of chronic stress. Individuals with higher stress appeared to be in poorer condition, as indicated by fat scores and residual body mass. Prevalence of blood parasites was generally high and was highest in reserved habitat (59%) where miners were absent. Birds with blood parasites living in these habitats had higher H:L ratios but the intensity of infection and H:L ratio was inversely related. Our results suggest that birds persisting in the presence of noisy miners might experience chronic stress, but further study is necessary to separate the relative importance of noisy miner aggression from other potential stressors in small patches of degraded woodland. Stress induced by interspecific aggression should be considered in future studies of wildlife living in remnant vegetation.
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- 2019
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15. Relative demographic susceptibility does not explain the extinction chronology of Sahul’s megafauna
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Christopher N. Johnson, Frédérik Saltré, Giovanni Strona, John Llewelyn, Corey J. A. Bradshaw, Vera Weisbecker, Ecological Data Science, Organismal and Evolutionary Biology Research Programme, and Faculty of Biological and Environmental Sciences
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0106 biological sciences ,0301 basic medicine ,LIFE-HISTORY ,AUSTRALIA ,01 natural sciences ,Predation ,INFERRING EXTINCTION ,CONFIDENCE-INTERVALS ,LATE PLEISTOCENE ,Extant taxon ,Megafauna ,Taxonomic rank ,Biology (General) ,History, Ancient ,BODY-SIZE ,Mammals ,RISK ,0303 health sciences ,Vombatiformes ,Ecology ,biology ,Fossils ,extinction ,General Neuroscience ,General Medicine ,musculoskeletal system ,humanities ,Vertebrates ,1181 Ecology, evolutionary biology ,Medicine ,macropodiformes ,geographic locations ,Research Article ,carnivores ,QH301-705.5 ,Climate Change ,Science ,Climate change ,METABOLISM ,Extinction, Biological ,flightless birds ,010603 evolutionary biology ,General Biochemistry, Genetics and Molecular Biology ,Birds ,03 medical and health sciences ,Animals ,Humans ,natural sciences ,Demography ,030304 developmental biology ,LATE QUATERNARY MEGAFAUNA ,New Guinea ,Herbivore ,Extinction ,General Immunology and Microbiology ,Paleontology ,marsupial ,social sciences ,Models, Theoretical ,15. Life on land ,biology.organism_classification ,POPULATION VIABILITY ANALYSIS ,030104 developmental biology ,Population viability analysis ,13. Climate action ,Other ,vombatiformes ,Chronology - Abstract
The causes of Sahul’s megafauna extinctions remain uncertain, although several interacting factors were likely responsible. To examine the relative support for hypotheses regarding plausible ecological mechanisms underlying these extinctions, we constructed the first stochastic, age-structured models for 13 extinct megafauna species from five functional/taxonomic groups, as well as 8 extant species within these groups for comparison. Perturbing specific demographic rates individually, we tested which species were more demographically susceptible to extinction, and then compared these relative sensitivities to the fossil-derived extinction chronology. Our models show that the macropodiformes were the least demographically susceptible to extinction, followed by carnivores, monotremes, vombatiform herbivores, and large birds. Five of the eight extant species were as or more susceptible than the extinct species. There was no clear relationship between extinction susceptibility and the extinction chronology for any perturbation scenario, while body mass and generation length explained much of the variation in relative risk. Our results reveal that the actual mechanisms leading to the observed extinction chronology were unlikely related to variation in demographic susceptibility per se, but were possibly driven instead by finer-scale variation in climate change and/or human prey choice and relative hunting success.
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- 2021
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16. The effects of weather variability on patterns of genetic diversity in Tasmanian bettongs
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Christopher N. Johnson, Matthew Pauza, Christopher P. Burridge, Menna E. Jones, Kirstin M. Proft, and Brooke L. Bateman
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0106 biological sciences ,0301 basic medicine ,Range (biology) ,Climate Change ,Population ,Species distribution ,Population Dynamics ,Population genetics ,Climate change ,Biology ,010603 evolutionary biology ,01 natural sciences ,03 medical and health sciences ,Potoroidae ,Genetics ,Animals ,education ,Relative species abundance ,Weather ,Ecology, Evolution, Behavior and Systematics ,Ecosystem ,education.field_of_study ,Genetic diversity ,Ecology ,Genetic Variation ,respiratory system ,15. Life on land ,030104 developmental biology ,13. Climate action ,population characteristics ,Spatial variability ,human activities - Abstract
While the effects of climate (long‐term, prevailing weather) on species abundance, range and genetic diversity have been widely studied, short‐term, localized variations in atmospheric conditions (i.e., weather) can also rapidly alter species’ geographical ranges and population sizes, but little is known about how they affect genetic diversity. We investigated the relationship between weather and range‐wide genetic diversity in a marsupial, Bettongia gaimardi, using dynamic species distribution models (SDMs). Genetic diversity was lower in parts of the range where the weather‐based SDM predicted high variability in probability of B. gaimardi occurrence during 1950–2009. This is probably an effect of lower population sizes and extinction–recolonization cycles in places with highly variable weather. Spatial variation in genetic diversity was also better predicted by mean probabilities of B. gaimardi occurrence from weather‐ than climate‐based SDMs. Our results illustrate the importance of weather in driving population dynamics and species distributions on decadal timescales and thereby in affecting genetic diversity. Modelling the links between changing weather patterns, species distributions and genetic diversity will allow researchers to better forecast biological impacts of climate change.
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- 2021
17. Roughing it: terrain is crucial in identifying novel translocation sites for the vulnerable brush-tailed rock-wallaby (Petrogale pencillata)
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Barry W. Brook, Christopher N. Johnson, and Shane D. Morris
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0106 biological sciences ,Australian mega-fires ,Species distribution ,Population ,010603 evolutionary biology ,01 natural sciences ,Invasive species ,Predation ,assisted migration ,education ,lcsh:Science ,conservation translocation ,species distribution models ,education.field_of_study ,Ecology, Conservation, and Global Change Biology ,Multidisciplinary ,Extinction ,biology ,Ecology ,010604 marine biology & hydrobiology ,Rock-wallaby ,15. Life on land ,biology.organism_classification ,Habitat ,Threatened species ,lcsh:Q ,ecological modelling ,Research Article - Abstract
Translocations—the movement of species from one place to another—are likely to become more common as conservation attempts to protect small isolated populations from threats posed by extreme events such as bushfires. The recent Australian mega-fires burnt almost 40% of the habitat of the brush-tailed rock-wallaby (Petrogale pencillata), a threatened species whose distribution is already restricted, primarily due to predation by invasive species. This chronic threat of over-predation, coupled with the possible extinction of the genetically distinct southern population (approx. 40 individuals in the wild), makes this species a candidate for a conservation translocation. Here, we use species distribution models to identify translocation sites for the brush-tailed rock-wallaby. Our models exhibited high predictive accuracy, and show that terrain roughness, a surrogate for predator refugia, is the most important variable. Tasmania, which currently has no rock-wallabies, showed high suitability and is fox-free, making it a promising candidate site. We outline our argument for the trial translocation of rock-wallaby to Maria Island, located off Tasmania's eastern coast. This research offers a transparent assessment of the translocation potential of a threatened species, which can be adapted to other taxa and systems.
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- 2020
18. Harnessing the power of ecological interactions to reduce the impacts of feral cats
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Calum X. Cunningham, Menna E. Jones, and Christopher N. Johnson
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0106 biological sciences ,Global and Planetary Change ,CATS ,Ecology ,010604 marine biology & hydrobiology ,Ecology (disciplines) ,Biology ,010603 evolutionary biology ,01 natural sciences ,Invasive species ,Predation ,Felis catus ,Biological sciences ,Nature and Landscape Conservation - Abstract
Cats (Felis catus) are globally one of the most widespread invasive predators and are identified as one of the top 100 invasive species (Lowe et al. 2000). The effects of cats are particularly seve...
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- 2019
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19. Enabling synthesis in fragment-based drug discovery by reactivity mapping: photoredox-mediated cross-dehydrogenative heteroarylation of cyclic amines
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Steven V. Ley, Fabio Mitsuo Lima, Christopher N. Johnson, Rachel Grainger, and Tom D. Heightman
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010405 organic chemistry ,Ligand ,Drug discovery ,Chemistry ,Fragment-based lead discovery ,General Chemistry ,010402 general chemistry ,Ring (chemistry) ,01 natural sciences ,Combinatorial chemistry ,0104 chemical sciences ,Fragment (logic) ,Reactivity (chemistry) ,Target protein ,Cyclic amines - Abstract
In fragment-based drug discovery (FBDD), a weakly binding fragment hit is elaborated into a potent ligand by bespoke functionalization along specific directions (growth vectors) from the fragment core in order to complement the 3D structure of the target protein. This structure-based design approach can present significant synthetic challenges, as growth vectors often originate on sp2 or sp3 ring carbons which are not the most synthetically accessible points on the fragment. To address this issue and expedite synthesis in FBDD, we established a nanogram-to-gram workflow for the development of enabling synthetic transformations, such as the direct C–H functionalization of heterocycles. This novel approach deploys high-throughput experimentation (HTE) in 1536-well microtiter plates (MTPs) facilitated by liquid handling robots to screen reaction conditions on the nanomolar scale; subsequently the reaction is upscaled in a continuous flow to generate gram-quantities of the material. In this paper, we disclose the use of this powerful workflow for the development of a photoredox-mediated cross-dehydrogenative coupling of fragments and medicinally relevant heterocyclic precursors via Minisci-type addition of α-amino radicals to electron-deficient heteroarenes. The optimized reaction conditions were employed on the milligram-scale on a diverse set of 112 substrates to map out structure–reactivity relationships (SRRs) of the transformation. The coupling exhibits excellent tolerance to a variety of functional groups and N-rich heteroarenes relevant to FBDD and was upscaled in a continuous flow to afford gram-quantities of pharmaceutically relevant sp2–sp3 privileged architectures.
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- 2019
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20. Impacts of feral horses in the Australian Alps and evidence‐based solutions
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Hugh Allan, Chloe F. Sato, Euan G. Ritchie, Geoffrey Hope, David J. Paull, Don A. Driscoll, R. Williams, Sam C. Banks, Renee Hartley, Brendan Mackey, Christopher N. Johnson, Tim S. Doherty, Luciana L. Porfirio, Nicholas J. Beeton, Susanna Venn, David M. Watson, Deirdre Slattery, Maggie J. Watson, Mark Lintermans, Rebecca C Cherubin, Jamie Pittock, Graeme L. Worboys, Ben C. Scheele, C. Max Finlayson, and Ken Green
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0106 biological sciences ,animal diseases ,010604 marine biology & hydrobiology ,media_common.quotation_subject ,Small population size ,Culling ,Management, Monitoring, Policy and Law ,010603 evolutionary biology ,01 natural sciences ,Population control ,Invasive species ,Fishery ,Critically endangered ,Threatened species ,Protected area ,Welfare ,Ecology, Evolution, Behavior and Systematics ,Nature and Landscape Conservation ,media_common - Abstract
New evidence of impacts by feral horses in Australia's alpine parks systems confirms they endanger threatened species and extensively damage critically endangered bog communities that could take millennia to recover. These impacts are not confounded by effects of deer and accumulate over time, even when only a small number of feral horses (~100) are present. With protected areas representing only a small proportion of the area of the Australian states of New South Wales (9.3%) and Victoria (17%), allowing feral horses to degrade reserves is not a reasonable management compromise, is contrary to the purpose of the protected area system and conflicts with international obligations. Modelling and decades of management experience indicate that trapping alone does not control feral horse numbers. Trapping and fertility control can work in small populations, but not when there are several thousand horses in remote areas. Aerial culling is needed to cost-effectively and humanely control feral horse populations. The relatively small amount of suffering feral horses experience during a cull is outweighed by (i) avoiding suffering and death of horses from starvation and thirst, (ii) avoiding the suffering of native animals displaced by horses and (iii) avoiding the ethical concerns of driving threatened species towards extinction. Objections to aerial culling on welfare and cultural grounds are contradicted by evidence. Improving knowledge in the general community about what is at stake is long overdue because without this knowledge, small groups with vested interests and unfounded claims have been able to dominate debate and dictate management actions. As a result of ineffective management, horse populations are now expanding and causing well-documented damage to Australia's alpine parks, placing at risk almost $10M spent on restoration after livestock grazing ended. The costs of horse control and restoration escalate the longer large horse populations remain in the alpine parks. It is crucial that feral horse numbers are rapidly reduced to levels where ecosystems begin to recover. Aerial culling is needed as part of the toolbox to achieve that reduction.
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- 2019
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21. Modelling horse management in the Australian Alps
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Christopher N. Johnson and Nicholas J. Beeton
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0106 biological sciences ,education.field_of_study ,business.industry ,010604 marine biology & hydrobiology ,Population size ,Environmental resource management ,Population ,Culling ,Management, Monitoring, Policy and Law ,010603 evolutionary biology ,01 natural sciences ,Population control ,Adaptive management ,Geography ,Population model ,Bioregion ,Population growth ,business ,education ,Ecology, Evolution, Behavior and Systematics ,Nature and Landscape Conservation - Abstract
Management of the feral Horse (Equus caballus) in the Australian Alps bioregion is a difficult and emotive issue, with interested parties working from vastly differing perspectives. Compounding this, information regarding ecology and distribution of horses, and the cost and effectiveness of management strategies is often unknown or uncertain. Resolving these issues requires an objective approach with the flexibility to incorporate different potential scenarios. We used a spatially explicit population model to compare the potential effects of two different management strategies on populations of horses in the Australian Alps bioregion: culling from helicopters versus trapping and mustering. We populated the model using the results of population surveys conducted in 2014, vegetation data and cost estimates. We then provided an estimate of the effect of each strategy on population size across the Alps, and their corresponding costs, compared to no management. To account for uncertainties, we simulated different scenarios for horse population densities, dispersal rates and population growth rates. Management using aerial culling was more effective than mustering in every scenario modelled, and three to six times cheaper. Aerial culling was only slightly more effective within its control region. However, because mustering is necessarily restricted by road access, this translated to a substantial improvement in population control – up to 2000 horses where growth and dispersal rates were high. Our results unequivocally suggest aerial culling as the only strategy that could effectively control horses within the modelled range of scenarios; this result stands in addition to its other potential benefits of lower cost, animal stress and landscape disturbance. A major advantage of this modelling approach is that we can easily update it with new data, test different measures of effectiveness and add new scenarios to adapt to the rapidly changing situation on the ground, both in terms of the ecology and the political climate.
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- 2019
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22. Fragment-to-Lead Medicinal Chemistry Publications in 2017
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Wolfgang Jahnke, Christopher N. Johnson, Iwan J. P. de Esch, Daniel A. Erlanson, and Paul N. Mortenson
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010404 medicinal & biomolecular chemistry ,0303 health sciences ,03 medical and health sciences ,Information retrieval ,Lead (geology) ,Fragment (logic) ,Chemistry ,Drug Discovery ,Molecular Medicine ,01 natural sciences ,030304 developmental biology ,0104 chemical sciences - Abstract
This Miniperspective is the third in a series reviewing fragment-to-lead publications from a given year. Following our reviews for 2015 and 2016, this Miniperspective provides tabulated summaries of relevant articles published in 2017 along with some general observations. In addition, we discuss insights obtained from analysis of the combined data set of 85 examples from all three years of publications.
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- 2018
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23. Habitat amount and quality, not patch size, determine persistence of a woodland-dependent mammal in an agricultural landscape
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Glen C. Bain, Rowena Hamer, Menna E. Jones, Riana Gardiner, and Christopher N. Johnson
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0106 biological sciences ,Ecology ,biology ,Occupancy ,Insular biogeography ,010604 marine biology & hydrobiology ,Bettongia gaimardi ,fungi ,Geography, Planning and Development ,Bettong ,Woodland ,15. Life on land ,biology.organism_classification ,010603 evolutionary biology ,01 natural sciences ,Geography ,Habitat ,Landscape ecology ,Nature and Landscape Conservation ,Wildlife conservation - Abstract
The classical theory of island biogeography explains loss of species in fragmented landscapes as an effect of remnant patch size and isolation. Recently this has been challenged by the habitat amount and habitat continuum hypotheses, according to which persistence in modified landscapes is related to total habitat amount rather than habitat configuration or the ability of species to use all habitats to varying degrees. Distinguishing between these theories is essential for effective conservation planning in modified landscapes. Identify which factors of habitat type, amount and configuration predict the persistence of a keystone woodland specialist, the eastern bettong Bettongia gaimardi, in a fragmented landscape. In the Midlands region of Tasmania we carried out camera surveys at 62 sites in summer and winter. We included habitat and landscape features to model whether habitat amount or patch size and isolation influenced the presence of the eastern bettong, and to measure effects of habitat quality. Habitat amount within a 1 km buffer was a better predictor of occupancy than patch size and isolation. Occupancy was also affected by habitat quality, indicated by density of regenerating stems. Our results support the habitat amount hypothesis as a better predictor of presence. For a species that is able to cross the matrix between remnant patches and utilise multiple patches, the island biogeography concept does not explain habitat use in fragmented landscapes. Our results emphasize the value of small remnant patches for conservation of the eastern bettong, provided those patches are in good condition.
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- 2018
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24. An exotic woody weed in a pastoral landscape provides habitat for many native species, but has no apparent threatened species conservation significance
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Leon A. Barmuta, Christopher N. Johnson, Jamie B. Kirkpatrick, Claire E. Ranyard, and Menna E. Jones
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0106 biological sciences ,biology ,Ecology ,010604 marine biology & hydrobiology ,Endangered species ,Biodiversity ,Species diversity ,Introduced species ,15. Life on land ,Management, Monitoring, Policy and Law ,biology.organism_classification ,010603 evolutionary biology ,01 natural sciences ,Ulex europaeus ,Geography ,Abundance (ecology) ,Threatened species ,Species richness ,Ecology, Evolution, Behavior and Systematics ,Nature and Landscape Conservation - Abstract
Exotic woody plants are often used by native organisms, but may also be targets of expensive control justified by nature conservation. We determine the use of a weed of national significance, Gorse (Ulex europaeus L.), by native mammals, birds, reptiles and vascular plants in pastoral areas in an Australian biodiversity hotspot. Large numbers of fauna species were observed using Gorse within our 43 × 1 ha sample sites in riparian, woodland and pasture vegetation. Gorse cover and/or height positively influenced: the detection of mammals as a whole in an interaction with visibility at 50-75 cm above ground, but not their species richness or individual species abundances; bird abundance, but not richness; and, reptile richness but not abundance. In terms of flora, Gorse cover and/or height positively affected: non‐native plant species richness and the height and fecundity, but not the richness, of native grasses and forbs - but Gorse cover negatively influenced the height of native herbs. The only species of conservation significance using Gorse were three mammals, only one of which, the Tasmanian Pademelon (Thylogale billardieri), was sufficiently common to analyse. Its abundance had no relationship with Gorse cover or height. Even in the wider context of complementary work, there is no strong threatened species conservation justification for retaining Gorse thickets in the Northern Midlands pastoral landscape. Equally, expending scarce conservation resources to remove Gorse, as is taking place, is unlikely to achieve any threatened species conservation outcome but may help reduce long‐term loss of native animal and plant species.
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- 2018
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25. A Fragment-Derived Clinical Candidate for Antagonism of X-Linked and Cellular Inhibitor of Apoptosis Proteins: 1-(6-[(4-Fluorophenyl)methyl]-5-(hydroxymethyl)-3,3-dimethyl-1H,2H,3H-pyrrolo[3,2-b]pyridin-1-yl)-2-[(2R,5R)-5-methyl-2-([(3R)-3-methylmorpholin-4-yl]methyl)piperazin-1-yl]ethan-1-one (ASTX660)
- Author
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Gianni Chessari, Ildiko Maria Buck, Edward J. Lewis, Elisabetta Chiarparin, Jong Sook Ahn, Gordon Saxty, Anna Hopkins, Nicola E. Wilsher, Michael Reader, George Ward, Torren M. Peakman, Steven Howard, Pamela A. Williams, Tomoko Smyth, Christopher N. Johnson, Neil T. Thompson, Vanessa Martins, Joanne M. Munck, Alessia Millemaggi, James Edward Harvey Day, Lee William Page, and Sharna J. Rich
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010405 organic chemistry ,Peptidomimetic ,Stereochemistry ,Antagonist ,Inhibitor of apoptosis ,01 natural sciences ,0104 chemical sciences ,XIAP ,03 medical and health sciences ,chemistry.chemical_compound ,0302 clinical medicine ,chemistry ,Apoptosis ,030220 oncology & carcinogenesis ,Drug Discovery ,Molecular Medicine ,Hydroxymethyl ,Selectivity ,Antagonism - Abstract
Inhibitor of apoptosis proteins (IAPs) are promising anticancer targets, given their roles in the evasion of apoptosis. Several peptidomimetic IAP antagonists, with inherent selectivity for cellular IAP (cIAP) over X-linked IAP (XIAP), have been tested in the clinic. A fragment screening approach followed by structure-based optimization has previously been reported that resulted in a low-nanomolar cIAP1 and XIAP antagonist lead molecule with a more balanced cIAP–XIAP profile. We now report the further structure-guided optimization of the lead, with a view to improving the metabolic stability and cardiac safety profile, to give the nonpeptidomimetic antagonist clinical candidate 27 (ASTX660), currently being tested in a phase 1/2 clinical trial (NCT02503423).
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- 2018
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26. Making the connection: expanding the role of restoration genetics in restoring and evaluating connectivity
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Menna E. Jones, Christopher N. Johnson, Kirstin M. Proft, and Christopher P. Burridge
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0106 biological sciences ,0301 basic medicine ,Conservation genetics ,Genetic diversity ,Ecology ,Resistance (ecology) ,Computer science ,Seven Management and Planning Tools ,Population size ,15. Life on land ,010603 evolutionary biology ,01 natural sciences ,03 medical and health sciences ,030104 developmental biology ,Biological dispersal ,Environmental planning ,Restoration ecology ,Ecology, Evolution, Behavior and Systematics ,Nature and Landscape Conservation ,Landscape connectivity - Abstract
The success of restoration activities is affected by connectivity with the surrounding landscape. From a genetic perspective, landscape connectivity can influence gene flow, effective size, and genetic diversity of populations, which in turn have impacts on the fitness and adaptive potential of species in restored areas. Researchers and practitioners are increasingly using genetic data to incorporate elements of connectivity into restoration planning and evaluation. We show that genetic studies of connectivity can improve restoration planning in three main ways. First, by comparing genetic estimates of contemporary and historical gene flow and population size, practitioners can establish historical baselines that may provide targets for restoration of connectivity. Second, empirical estimates of dispersal, landscape resistance to movement, and adaptive genetic variance can be derived from genetic data and used to parameterize existing restoration planning tools. Finally, restoration actions can also be targeted to remove barriers to gene flow or mitigate pinch-points in corridors. We also discuss appropriate methods for evaluating the restoration of gene flow over timescales required by practitioners. Collaboration between restoration geneticists, ecologists, and practitioners is needed to develop practical and innovative ways to further incorporate connectivity into restoration practice.
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- 2018
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27. Fragment-to-Lead Medicinal Chemistry Publications in 2016
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Wolfgang Jahnke, Paul N. Mortenson, David C. Rees, Christopher N. Johnson, and Daniel A. Erlanson
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0301 basic medicine ,Resource (biology) ,010405 organic chemistry ,Drug discovery ,Chemistry ,Bioinformatics ,01 natural sciences ,Data science ,0104 chemical sciences ,03 medical and health sciences ,030104 developmental biology ,Lead (geology) ,Fragment (logic) ,Drug Discovery ,Molecular Medicine - Abstract
The popularity of fragment-based drug discovery (FBDD) is demonstrated by the number of recent successful fragment-to-lead (F2L) publications. This Miniperspective provides a tabulated summary of the F2L literature published in the year 2016, along with discussion of general trends. It uses the same format as our summary of the 2015 literature and is intended to be a resource for both FBDD practitioners and medicinal chemists in general.
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- 2017
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28. Ecological and evolutionary legacy of megafauna extinctions
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Mathias M. Pires, Robert J. Marquis, Thomas Pape, Elizabeth Nichols, Dennis M. Hansen, Paulo R. Guimarães, Mauro Galetti, Norman Owen-Smith, Marcos Moleón, Jens M. Olesen, Pedro Jordano, Jens-Christian Svenning, Michael Munk, Jacqueline S. de Mattos, Andreas H. Schweiger, and Christopher N. Johnson
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0106 biological sciences ,0301 basic medicine ,Extinction ,Ecology ,Biology ,Commensalism ,010603 evolutionary biology ,01 natural sciences ,General Biochemistry, Genetics and Molecular Biology ,Predation ,03 medical and health sciences ,030104 developmental biology ,Anthropocene ,Megafauna ,Paleoecology ,General Agricultural and Biological Sciences ,Domestication ,Trophic cascade - Abstract
For hundreds of millions of years, large vertebrates (megafauna) have inhabited most of the ecosystems on our planet. During the late Quaternary, notably during the Late Pleistocene and the early Holocene, Earth experienced a rapid extinction of large, terrestrial vertebrates. While much attention has been paid to understanding the causes of this massive megafauna extinction, less attention has been given to understanding the impacts of loss of megafauna on other organisms with whom they interacted. In this review, we discuss how the loss of megafauna disrupted and reshaped ecological interactions, and explore the ecological consequences of the ongoing decline of large vertebrates. Numerous late Quaternary extinct species of predators, parasites, commensals and mutualistic partners were associated with megafauna and were probably lost due to their strict dependence upon them (co-extinctions). Moreover, many extant species have megafauna-adapted traits that provided evolutionary benefits under past megafauna-rich conditions, but are now of no or limited use (anachronisms). Morphological evolution and behavioural changes allowed some of these species partially to overcome the absence of megafauna. Although the extinction of megafauna led to a number of co-extinction events, several species that likely co-evolved with megafauna established new interactions with humans and their domestic animals. Species that were highly specialized in interactions with megafauna, such as large predators, specialized parasites, and large commensalists (e.g. scavengers, dung beetles), and could not adapt to new hosts or prey were more likely to die out. Partners that were less megafauna dependent persisted because of behavioural plasticity or by shifting their dependency to humans via domestication, facilitation or pathogen spill-over, or through interactions with domestic megafauna. We argue that the ongoing extinction of the extant megafauna in the Anthropocene will catalyse another wave of co-extinctions due to the enormous diversity of key ecological interactions and functional roles provided by the megafauna.
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- 2017
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29. Prey use by dingoes in a contested landscape: Ecosystem service provider or biodiversity threat?
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Bradley C. Congdon, Christopher M. Wurster, Damian S. Morrant, Christopher N. Johnson, and James R.A. Butler
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0106 biological sciences ,predator ,Biodiversity ,Bayesian mixing model ,010603 evolutionary biology ,01 natural sciences ,Canis lupus dingo ,anthropogenic ,Predation ,Common species ,biology.animal ,stable isotope ,Ecology, Evolution, Behavior and Systematics ,Original Research ,Nature and Landscape Conservation ,Apex predator ,Ecology ,biology ,carnivore ,conservation ,habitat use ,15. Life on land ,biology.organism_classification ,010601 ecology ,Habitat ,13. Climate action ,Threatened species ,Dingo ,diet ,rainforest - Abstract
In Australia, dingoes (Canis lupus dingo) have been implicated in the decline and extinction of a number of vertebrate species. The lowland Wet Tropics of Queensland, Australia is a biologically rich area with many species of rainforest‐restricted vertebrates that could be threatened by dingoes; however, the ecological impacts of dingoes in this region are poorly understood. We determined the potential threat posed by dingoes to native vertebrates in the lowland Wet Tropics using dingo scat/stomach content and stable isotope analyses of hair from dingoes and potential prey species. Common mammals dominated dingo diets. We found no evidence of predation on threatened taxa or rainforest specialists within our study areas. The most significant prey species were northern brown bandicoots (Isoodon macrourus), canefield rats (Rattus sordidus), and agile wallabies (Macropus agilis). All are common species associated with relatively open grass/woodland habitats. Stable isotope analysis suggested that prey species sourced their nutrients primarily from open habitats and that prey choice, as identified by scat/stomach analysis alone, was a poor indicator of primary foraging habitats. In general, we find that prey use by dingoes in the lowland Wet Tropics does not pose a major threat to native and/or threatened fauna, including rainforest specialists. In fact, our results suggest that dingo predation on “pest” species may represent an important ecological service that outweighs potential biodiversity threats. A more targeted approach to managing wild canids is needed if the ecosystem services they provide in these contested landscapes are to be maintained, while simultaneously avoiding negative conservation or economic impacts.
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- 2017
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30. How many bird and mammal extinctions has recent conservation action prevented?
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Thomas M. Brooks, Ana S. L. Rodrigues, Ella Vázquez-Domínguez, Nicolette S. Roach, Diana O. Fisher, Tracey J. Regan, Friederike C. Bolam, Rosalind J. Kennerley, Matthew F. Child, Richard P. Young, Christopher N. Johnson, Louise Mair, Alexander C. Lees, John F. Lamoreux, Malin C. Rivers, Piero Visconti, Stuart H. M. Butchart, Philip J. K. McGowan, Hannah Wheatley, Jim J. Groombridge, Luis Miguel Renjifo, Claudia Hermes, Rob W. Martin, Birgit Fessl, Peter A. Cranswick, Mark A. Burgman, James R.S. Westrip, Javier Calzada, Tom Squires, Luc Lens, Stephen T. Garnett, David P. Mallon, Paul Salaman, Michael R. Hoffmann, Erik Meijaard, Marco Angelico, Sarah R. B. King, Federico Méndez-Sánchez, John C. Z. Woinarski, Alexandre Reis Percequillo, Carlo Rondinini, Chris R. Dickman, R. J. Safford, Lizanne Roxburgh, Simon P. Mahood, Yuliana Bedolla-Guzmán, School of Natural and Environmental Sciences, Newcastle University, Centre d’Ecologie Fonctionnelle et Evolutive (CEFE), Université Paul-Valéry - Montpellier 3 (UPVM)-École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud])-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut Agro - Montpellier SupAgro, Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro), Université Paul-Valéry - Montpellier 3 (UPVM)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud])-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), and Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)
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0106 biological sciences ,lcsh:QH1-199.5 ,IMPACT ,Biodiversity ,Delphi method ,extinction risk ,[SDV.BID]Life Sciences [q-bio]/Biodiversity ,lcsh:General. Including nature conservation, geographical distribution ,010603 evolutionary biology ,01 natural sciences ,Delphi ,IUCN Red List ,Convention on Biological Diversity ,14. Life underwater ,Aichi biodiversity target 12 ,Ecology, Evolution, Behavior and Systematics ,ComputingMilieux_MISCELLANEOUS ,Nature and Landscape Conservation ,Extinction ,Ecology ,010604 marine biology & hydrobiology ,species conservation ,PROTEÇÃO AMBIENTAL ,Biology and Life Sciences ,social sciences ,15. Life on land ,musculoskeletal system ,humanities ,Geography ,Action (philosophy) ,Threatened species ,method ,Mammal ,geographic locations - Abstract
Aichi Target 12 of the Convention on Biological Diversity (CBD) contains the aim to ‘prevent extinctions of known threatened species’. To measure the degree to which this was achieved, we used expert elicitation to estimate the number of bird and mammal species whose extinctions were prevented by conservation action in 1993–2020 (the lifetime of the CBD) and 2010–2020 (the timing of Aichi Target 12). We found that conservation action prevented 21–32 bird and 7–16 mammal extinctions since 1993, and 9–18 bird and two to seven mammal extinctions since 2010. Many remain highly threatened and may still become extinct. Considering that 10 bird and five mammal species did go extinct (or are strongly suspected to) since 1993, extinction rates would have been 2.9–4.2 times greater without conservation action. While policy commitments have fostered significant conservation achievements, future biodiversity action needs to be scaled up to avert additional extinctions.
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- 2020
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31. Small mammal diversity is higher in infrequently compared with frequently burnt rainforest–savanna mosaics in the north Kimberley, Australia
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David M. J. S. Bowman, Tom Vigilante, Hugh W. McGregor, Christopher N. Johnson, Catherine Goonack, Stefania Ondei, Angela M. Reid, Lynda D. Prior, and Desmond Williams
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0106 biological sciences ,010504 meteorology & atmospheric sciences ,Fire regime ,Ecology ,Context (language use) ,Rainforest ,Vegetation ,Management, Monitoring, Policy and Law ,010603 evolutionary biology ,01 natural sciences ,Dry season ,Vegetation type ,Species richness ,Transect ,Ecology, Evolution, Behavior and Systematics ,0105 earth and related environmental sciences - Abstract
Context Populations of native mammals are declining at an alarming rate in many parts of tropical northern Australia. Fire regimes are considered a contributing factor, but this hypothesis is difficult to test because of the ubiquity of fire. Aims This preliminary study investigated relative abundance and richness of small mammals on a gradient of fire regimes in the Uunguu Indigenous Protected Area (north Kimberley, Australia). Methods Species were sampled using 40 unbaited camera traps, positioned for a year on 20 transects crossing the rainforest–savanna boundary at locations with comparable environment and geology but varying fire history. The relative importance of the factors ‘fire frequency’, ‘late dry season fire frequency’, ‘time since burnt’ and ‘vegetation type’ as predictors of the number of small mammal species and detections was tested using Spatial Generalised Linear Mixed Models to account for spatial autocorrelation. Key results Nine species of small mammals were observed. Mammals were more abundant and diverse in locations with low overall fire frequency, which was a better predictor than late dry season fire frequency or time since burnt. The model including fire frequency and vegetation explained the highest proportion of total variation in mammal diversity (R2 = 42.0%), with most of this variation explained by fire frequency alone (R2 = 40.5%). The best model for number of detections (R2 = 20.9%) included both factors. Conclusions In the north Kimberley, small mammals are likely to be more abundant and diverse in areas with low fire frequency. Implications This natural experiment supports the theory that frequent fires are contributing to the decline of small mammals observed across northern Australia.
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- 2020
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32. Activity and social interactions in a wide-ranging specialist scavenger, the Tasmanian devil (Sarcophilus harrisii), revealed by animal-borne video collars
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Georgina E. Andersen, Christopher N. Johnson, Hugh W. McGregor, and Menna E. Jones
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0106 biological sciences ,Carnivora ,Predation ,Social Sciences ,01 natural sciences ,Agonistic behaviour ,Psychology ,Foraging ,Carnivore ,Mammals ,Multidisciplinary ,Ecology ,Animal Behavior ,Behavior, Animal ,Eutheria ,Eukaryota ,Agriculture ,Trophic Interactions ,010601 ecology ,Sarcophilus ,Community Ecology ,Vertebrates ,Medicine ,Research Article ,Livestock ,Science ,Zoology ,Context (language use) ,Biology ,010603 evolutionary biology ,Ecosystems ,Tasmanian devil ,Hunting Behavior ,Animals ,Interpersonal Relations ,Carrion ,Ecosystem ,Behavior ,Ecology and Environmental Sciences ,Organisms ,Biology and Life Sciences ,biology.organism_classification ,Marsupialia ,Amniotes ,Animals, Zoo - Abstract
Observing animals directly in the field provides the most accurate understanding of animal behaviour and resource selection. However, making prolonged observation of undisturbed animals is difficult or impossible for many species. To overcome this problem for the Tasmanian devil (Sarcophilus harrisii), a cryptic and nocturnal carnivore, we developed animal-borne video collars to investigate activity patterns, foraging behaviour and social interactions. We collected 173 hours of footage from 13 individual devils between 2013 and 2017. Devils were active mostly at night, and resting was the most common behaviour in all diel periods. Devils spent more time scavenging than hunting and exhibited opportunistic and flexible foraging behaviours. Scavenging occurred mostly in natural vegetation but also in anthropogenic vegetation and linear features (roads and fence lines). Scavenging frequency was inversely incremental with size e.g. small carcasses were scavenged most frequently. Agonistic interactions with conspecifics occurred most often when devils were traveling but also occurred over carcasses or dens. Interactions generally involved vocalisations and brief chases without physical contact. Our results highlight the importance of devils as a scavenger in the Tasmanian ecosystem, not just of large carcasses for which devils are well known but in cleaning up small items of carrion in the bush. Our results also show the complex nature of intraspecific interactions, revealing greater detail on the context in which interactions occur. In addition, this study demonstrates the benefits of using animal-borne imaging in quantifying behaviour of elusive, nocturnal carnivores not previously seen using conventional field methods.
- Published
- 2020
33. Micro Methods for Megafauna: Novel Approaches to Late Quaternary Extinctions and Their Contributions to Faunal Conservation in the Anthropocene
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Michael D. Petraglia, Emily L. Lindsey, Michael Bunce, Kristina Douglass, Judith Field, J. Tyler Faith, Frido Welker, Alexis M. Mychajliw, Natalia A. Villavicencio, Jillian A. Swift, Rachel Wood, Gifford H. Miller, Patrick Roberts, Nicole Boivin, Eline D. Lorenzen, Joe Dortch, Viviane Slon, Christopher N. Johnson, Michael R. Waters, Simon Haberle, Eileen Jacob, James A. Fellows Yates, and Julien Louys
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010506 paleontology ,0303 health sciences ,Extinction ,Ecology ,extinction ,Biodiversity ,interdisciplinary science ,conservation ,Climate change ,15. Life on land ,01 natural sciences ,Overview Articles ,03 medical and health sciences ,Ancient DNA ,megafauna ,Habitat ,13. Climate action ,Homo sapiens ,Anthropocene ,Megafauna ,General Agricultural and Biological Sciences ,030304 developmental biology ,0105 earth and related environmental sciences - Abstract
Drivers of Late Quaternary megafaunal extinctions are relevant to modern conservation policy in a world of growing human population density, climate change, and faunal decline. Traditional debates tend toward global solutions, blaming either dramatic climate change or dispersals of Homo sapiens to new regions. Inherent limitations to archaeological and paleontological data sets often require reliance on scant, poorly resolved lines of evidence. However, recent developments in scientific technologies allow for more local, context-specific approaches. In the present article, we highlight how developments in five such methodologies (radiocarbon approaches, stable isotope analysis, ancient DNA, ancient proteomics, microscopy) have helped drive detailed analysis of specific megafaunal species, their particular ecological settings, and responses to new competitors or predators, climate change, and other external phenomena. The detailed case studies of faunal community composition, extinction chronologies, and demographic trends enabled by these methods examine megafaunal extinctions at scales appropriate for practical understanding of threats against particular species in their habitats today.
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- 2019
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34. Animals as Agents in Fire Regimes
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Leonie E. Valentine, Claire N. Foster, Christopher N. Johnson, Sam C. Banks, David B. Lindenmayer, and Geoffrey J. Cary
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0106 biological sciences ,Herbivore ,010504 meteorology & atmospheric sciences ,Fire regime ,Ecology ,010603 evolutionary biology ,01 natural sciences ,Ecosystem engineer ,Environmental science ,Animals ,Ecosystem ,Fire ecology ,Ecology, Evolution, Behavior and Systematics ,0105 earth and related environmental sciences - Abstract
Fire is a powerful ecological and evolutionary force. Animals that modify drivers of fire behaviour could therefore have far-reaching effects on ecosystems. Yet, with a few notable exceptions, effects of animals on fire have been often overlooked. We show how animals can affect fire behaviour by modifying the amount, structure, or condition of fuel or, more rarely, by altering other controls on fire such as wind speed or ignition patterns. Some effects are readily observed and quantified. Others are more subtle but could be considerable when accumulated over time, space, and animal taxa. A combination of manipulative experiments, landscape studies, and multiscale fire models will be necessary to understand the consequences of widespread changes in animal populations for landscape fire.
- Published
- 2019
35. Factors affecting success of conservation translocations of terrestrial vertebrates: A global systematic review
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Shane D. Morris, Katherine E. Moseby, Christopher N. Johnson, and Barry W. Brook
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0106 biological sciences ,Reintroductions ,Ecology ,010604 marine biology & hydrobiology ,Psychological intervention ,Context (language use) ,Chromosomal translocation ,Biodiversity ,15. Life on land ,Biology ,010603 evolutionary biology ,01 natural sciences ,Invasive species ,Threatened species ,Translocations ,Population growth ,Global Change ,Diminishing returns ,Categorical variable ,Species conservation ,QH540-549.5 ,Ecology, Evolution, Behavior and Systematics ,Nature and Landscape Conservation ,Demography - Abstract
Translocation—moving individuals for releasein different locations—is among the most important conservation interventions for increasing or re-establishing populations of threatened species. However, translocations often fail. To improve their effectiveness, we need to understand the features that distinguish successful from failed translocations. We assembled and analysed a global database of translocations of terrestrial vertebrates(n=514)to assess the effects of various design features and extrinsic factors on success. We analysed outcomes usingstandardisedmetrics: a categorical success/failure classification; and population growth rate. Probability of categorical success and population growth rate increased with the total number of individuals released but with diminishing returns above about20–50individuals. Positive outcomes—categorical success and high population growth—were less likely for translocationsin Oceania, possibly because invasive species are a major threat in this region and are difficult to control at translocation sites. Rates of categorical success and population growth were higher in Europe and North America than elsewhere, suggesting the key role of context in positive translocation outcomes. Categorical success has increased throughout the20thcentury, but that increase may have plateaued at about 75% since about 1990. Our results suggest there is potential for further increase in the success of conservation translocations. This could be best achieved by greater investment in individual projects, as indicated by total number of animals released, which has not increased over time. Methods This data was compiled from the literature and a questionnaire. How this data was collected and processed is detailed in the paper. The attached code will run all analyses detailed in the paper. Usage Notes To replicate the results in their entirety you will likely need a supercomputer. A representative version of the results can be created by simply reducing the number of times the dataset it split (say from 1000 to 10).
- Published
- 2021
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36. Enumerating a continental-scale threat: How many feral cats are in Australia?
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Sarah Legge, Duncan R. Sutherland, Luke Woodford, F. Zewe, Teresa J. Eyre, Peter J. McDonald, Chris R. Dickman, Guy Ballard, Danielle Stokeld, William L. Geary, Anthony R. Rendall, Keith Morris, R. Paltridge, Hugh W. McGregor, Bronwyn A. Fancourt, Jesse Rowland, S. Hume, M. Maxwell, Euan G. Ritchie, John L. Read, Dale G. Nimmo, L. Greenwood, Maree Rich, Matthew Gentle, Rosemary Hohnen, David S. L. Ramsey, Daniel J. Ferguson, David M. Forsyth, Christopher N. Johnson, Graeme R. Gillespie, Thomas M. Newsome, John Augusteyn, Katherine E. Moseby, Brett P. Murphy, Adrian F. Wayne, Jeff Short, Marcus Baseler, Tony Buckmaster, John C. Z. Woinarski, Tom Doherty, and Glenn P. Edwards
- Subjects
0106 biological sciences ,education.field_of_study ,Ecology ,animal diseases ,Home range ,Fauna ,Population ,Wildlife ,Introduced species ,15. Life on land ,010603 evolutionary biology ,01 natural sciences ,Arid ,010601 ecology ,13. Climate action ,Feral cat ,Mainland ,education ,Ecology, Evolution, Behavior and Systematics ,Nature and Landscape Conservation - Abstract
Feral cats (Felis catus) have devastated wildlife globally. In Australia, feral cats are implicated in most recent mammal extinctions and continue to threaten native species. Cat control is a high-profile priority for Australian policy, research and management. To develop the evidence-base to support this priority, we first review information on cat presence/absence on Australian islands and mainland cat-proof exclosures, finding that cats occur across >99.8% of Australia's land area. Next, we collate 91 site-based feral cat density estimates in Australia and examine the influence of environmental and geographic influences on density. We extrapolate from this analysis to estimate that the feral cat population in natural environments fluctuates between 1.4 million (95% confidence interval: 1.0–2.3 million) after continent-wide droughts, to 5.6 million (95% CI: 2.5–11 million) after extensive wet periods. We estimate another 0.7 million feral cats occur in Australia's highly modified environments (urban areas, rubbish dumps, intensive farms). Feral cat densities are higher on small islands than the mainland, but similar inside and outside conservation land. Mainland cats reach highest densities in arid/semi-arid areas after wet periods. Regional variation in cat densities corresponds closely with attrition rates for native mammal fauna. The overall population estimate for Australia's feral cats (in natural and highly modified environments), fluctuating between 2.1 and 6.3 million, is lower than previous estimates, and Australian feral cat densities are lower than reported for North America and Europe. Nevertheless, cats inflict severe impacts on Australian fauna, reflecting the sensitivity of Australia's native species to cats and reinforcing that policy, research and management to reduce their impacts is critical.
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- 2017
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37. Protein Degradation by In-Cell Self-Assembly of Proteolysis Targeting Chimeras
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Christopher N. Johnson, Honorine Lebraud, David J. Wright, and Tom D. Heightman
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0301 basic medicine ,General Chemical Engineering ,Proteolysis ,Protein degradation ,01 natural sciences ,lcsh:Chemistry ,03 medical and health sciences ,Tetrazine ,chemistry.chemical_compound ,medicine ,medicine.diagnostic_test ,biology ,010405 organic chemistry ,Cereblon ,General Chemistry ,Ligand (biochemistry) ,0104 chemical sciences ,Cell biology ,Ubiquitin ligase ,030104 developmental biology ,chemistry ,Biochemistry ,lcsh:QD1-999 ,biology.protein ,Target protein ,Linker ,Research Article - Abstract
Selective degradation of proteins by proteolysis targeting chimeras (PROTACs) offers a promising potential alternative to protein inhibition for therapeutic intervention. Current PROTAC molecules incorporate a ligand for the target protein, a linker, and an E3 ubiquitin ligase recruiting group, which bring together target protein and ubiquitinating machinery. Such hetero-bifunctional molecules require significant linker optimization and possess high molecular weight, which can limit cellular permeation, solubility, and other drug-like properties. We show here that the hetero-bifunctional molecule can be formed intracellularly by bio-orthogonal click combination of two smaller precursors. We designed a tetrazine tagged thalidomide derivative which reacts rapidly with a trans-cyclo-octene tagged ligand of the target protein in cells to form a cereblon E3 ligase recruiting PROTAC molecule. The in-cell click-formed proteolysis targeting chimeras (CLIPTACs) were successfully used to degrade two key oncology targets, BRD4 and ERK1/2. ERK1/2 degradation was achieved using a CLIPTAC based on a covalent inhibitor. We expect this approach to be readily extendable to other inhibitor-protein systems because the tagged E3 ligase recruiter is capable of undergoing the click reaction with a suitably tagged ligand of any protein of interest to elicit its degradation., Tetrazine-tagged thalidomide derivatives undergo click reaction with trans-cyclo-octene-tagged protein ligands in cells: the resulting click-formed proteolysis-targeting chimeric molecule elicits ubiquitination and degradation of the target protein.
- Published
- 2016
38. Impacts and management of feral catsFelis catusin Australia
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Tim S. Doherty, Chris R. Dickman, Christopher N. Johnson, Sarah Legge, John C. Z. Woinarski, and Euan G. Ritchie
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0106 biological sciences ,Resource (biology) ,Ecology ,animal diseases ,Biology ,010603 evolutionary biology ,01 natural sciences ,Agricultural and Biological Sciences (miscellaneous) ,Invasive species ,Predation ,010601 ecology ,Threatened species ,Ecosystem management ,Feral cat ,Animal Science and Zoology ,Mainland ,Trophic cascade ,Ecology, Evolution, Behavior and Systematics - Abstract
Feral cats are among the most damaging invasive species worldwide, and are implicated in many extinctions, especially in Australia, New Zealand and other islands. Understanding and reducing their impacts is a global conservation priority. We review knowledge about the impacts and management of feral cats in Australia, and identify priorities for research and management. In Australia, the most well understood and significant impact of feral cats is predation on threatened mammals. Other impacts include predation on other vertebrates, resource competition, and disease transmission, but knowledge of these impacts remains limited. Lethal control is the most common form of management, particularly via specifically designed poison baits. Non-lethal techniques include the management of fire, grazing, food, and trophic cascades. Managing interactions between these processes is key to success. Given limitations on the efficacy of feral cat management, conservation of threatened mammals has required the establishment of insurance populations on predator-free islands and in fenced mainland enclosures. Research and management priorities are to: prevent feral cats from driving threatened species to extinction; assess the efficacy of new management tools; trial options for control via ecosystem management; and increase the potential for native fauna to coexist with feral cats.
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- 2016
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39. Fragment-to-Lead Medicinal Chemistry Publications in 2015
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Christopher N. Johnson, David C. Rees, Daniel A. Erlanson, and Christopher William Murray
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0301 basic medicine ,03 medical and health sciences ,030104 developmental biology ,Lead (geology) ,Fragment (logic) ,010405 organic chemistry ,Chemistry ,Drug Discovery ,Molecular Medicine ,01 natural sciences ,Medicinal chemistry ,0104 chemical sciences - Abstract
Fragment-based drug discovery (FBDD) is now well-established as a technology for generating new chemical leads and drugs. This Miniperspective provides a tabulated overview of the fragment-to-lead literature published in the year 2015, together with a commentary on trends observed across the FBDD field during this time. It is hoped that this tabulated summary will provide a useful point of reference for both FBDD practitioners and the wider medicinal chemistry community.
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- 2016
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40. Livestock guardian dogs as surrogate top predators? How Maremma sheepdogs affect a wildlife community
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Linda van Bommel and Christopher N. Johnson
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0106 biological sciences ,Sambar deer ,Wildlife ,010603 evolutionary biology ,01 natural sciences ,Predation ,Mesopredator release hypothesis ,large herbivore ,top predator ,mesopredator ,Trophic cascade ,Ecology, Evolution, Behavior and Systematics ,Original Research ,Nature and Landscape Conservation ,Apex predator ,Herbivore ,Ecology ,biology ,LGD ,business.industry ,biology.organism_classification ,trophic cascade ,010601 ecology ,LPD ,detection probability ,Livestock ,business - Abstract
Use of livestock guardian dogs (LGDs) to reduce predation on livestock is increasing. However, how these dogs influence the activity of wildlife, including predators, is not well understood. We used pellet counts and remote cameras to investigate the effects of free ranging LGDs on four large herbivores (eastern gray kangaroo, common wombat, swamp wallaby, and sambar deer) and one mesopredator (red fox) in Victoria, Australia. Generalized mixed models and one‐ and two‐species detection models were used to assess the influence of the presence of LGDs on detection of the other species. We found avoidance of LGDs in four species. Swamp wallabies and sambar deer were excluded from areas occupied by LGDs; gray kangaroos showed strong spatial and temporal avoidance of LGD areas; foxes showed moderately strong spatial and temporal avoidance of LGD areas. The effect of LGDs on wombats was unclear. Avoidance of areas with LGDs by large herbivores can benefit livestock production by reducing competition for pasture and disease transmission from wildlife to livestock, and providing managers with better control over grazing pressure. Suppression of mesopredators could benefit the small prey of those species. Synthesis and applications: In pastoral areas, LGDs can function as a surrogate top‐order predator, controlling the local distribution and affecting behavior of large herbivores and mesopredators. LGDs may provide similar ecological functions to those that in many areas have been lost with the extirpation of native large carnivores.
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- 2016
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41. Biodiversity friend or foe: land use by a top predator, the dingo in contested landscapes of the Australian Wet Tropics
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Christopher N. Johnson, Damian S. Morrant, Bradley C. Congdon, and James R.A. Butler
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0106 biological sciences ,Ecology ,biology ,Sclerophyll ,Biodiversity ,Introduced species ,15. Life on land ,010603 evolutionary biology ,01 natural sciences ,Predation ,Ecosystem services ,010601 ecology ,Geography ,Habitat ,biology.animal ,Dingo ,14. Life underwater ,Ecology, Evolution, Behavior and Systematics ,Apex predator - Abstract
Dingoes (Canis dingo) in the coastal lowlands of Australia's Wet Tropics are perceived as a major threat to biodiversity and subjected to broad-spectrum lethal control. However, evidence of their impacts is equivocal, and control programmes generally ignore the ecological benefits that dingoes might provide. Previous diet analysis has shown that dingoes in the Wet Tropics primarily prey on common, terrestrial mammals. However, little is known of dingo habitat use or prey acquisition in the region despite these activities having major implications for biodiversity conservation. We investigated land use by dingoes in the lowland Wet Tropics to enable predictions of potential prey types, relative prey use and modes of prey acquisition. Nine dingoes were tracked for 3–6 months. Home ranges and resting areas were estimated using multiple estimators, and habitat use was analysed using compositional analysis of habitat use and generalized additive models. Dingo ranging behaviour suggested that anthropogenic food subsidies were infrequently used. Each territory comprised several sclerophyll forest rest areas with adjacent sugarcane-grassland high activity areas. Individuals used each rest-activity area for extended durations before moving on to another. Sclerophyll and rainforests, which contain the fauna species of primary conservation concern, were generally used for rest/sleep, or movement between rest-activity areas. Activity patterns were consistent with dingoes hunting in open sugarcane-grassland habitats during daylight hours. Dingo activity was low in areas where fauna species of conservation concern occur, which suggests that dingoes do not pose a threat to their survival. Consequently, current broad-spectrum lethal control may have minimal benefits or even incur costs for biodiversity. Maximizing the ecosystem services provided by dingoes while simultaneously minimizing their negative impacts requires a more targeted location-specific management approach, one that assesses and mitigates impacts specifically where background circumstances suggest particular packs may be either a conservation or economic threat.
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- 2016
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42. Sympatric predator odour reveals a competitive relationship in size-structured mammalian carnivores
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Georgina E. Andersen, Christopher N. Johnson, and Menna E. Jones
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0106 biological sciences ,Dasyurus maculatus ,biology ,Ecology ,010604 marine biology & hydrobiology ,Zoology ,Interspecific competition ,15. Life on land ,biology.organism_classification ,010603 evolutionary biology ,01 natural sciences ,Vigilance (behavioural ecology) ,Animal ecology ,Feral cat ,Animal Science and Zoology ,14. Life underwater ,Quoll ,Carnivore ,Predator ,Ecology, Evolution, Behavior and Systematics - Abstract
Interspecific competition between sympatric carnivores can have a profound effect on the structure, function and composition of ecosystems. Interspecific competition is often asymmetrical and the smaller carnivore is usually affected the most. We investigated the behavioural responses of two native species, the larger Tasmanian devil (Sarcophilus harrisii) and the smaller spotted-tailed quoll (Dasyurus maculatus) to each other’s odour and to that of an introduced predator, the feral cat (Felis catus), in north-west Tasmania, Australia. We used an experimental array of camera traps, in which carnivore scats were added as treatments. Behavioural responses exhibited by devils and quolls are indicative of a dominant predator-mesopredator relationship and suggest the potential for interspecific competition. The larger predator, the devil, was as vigilant at quoll odour as at control camera traps, but showed decreased vigilance at cat odour and did not avoid cat or quoll odours. The smaller predator, the spotted-tailed quoll, increased its vigilance near devil odour compared to control camera traps but did not avoid it. This experiment shows that assessing the behavioural responses of sympatric carnivores to each other’s odour can help understand predator interactions and reveal the potential for interspecific competition. Understanding these interactions is crucial in managing and conserving carnivores. Animals navigate through an environment full of faecal odours left by predators, competitors and conspecifics. These odours provide information on both the immediate presence and the indirect risk of encountering a predator or an aggressive competitor. Tasmania’s largest predator, the Tasmanian devil, coexists with the smaller spotted-tailed quoll and the introduced feral cat. We tested the behavioural responses of Tasmanian devils and spotted-tailed quolls to each other’s faecal odour and to cat faecal odour. Behavioural patterns exhibited by predators in this experiment are indicative of a dominant predator-mesopredator relationship and suggest the potential for interspecific competition. Knowledge of the ecological interactions amongst sympatric carnivores can aid managers in making more informed decisions when trying to achieve specific conservation goals.
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- 2016
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43. Rainfall and topography predict gene flow among populations of the declining northern quoll (Dasyurus hallucatus)
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Christopher P. Burridge, Rosemary Hohnen, Peter S. Spencer, Sarah Legge, Christopher N. Johnson, Mia J. Hillyer, Ian J. Radford, and Katherine Tuft
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0106 biological sciences ,0301 basic medicine ,Herbivore ,education.field_of_study ,biology ,Ecology ,Population ,Biodiversity ,biology.organism_classification ,010603 evolutionary biology ,01 natural sciences ,03 medical and health sciences ,030104 developmental biology ,Habitat ,Threatened species ,Genetic structure ,Genetics ,Quoll ,education ,Ecology, Evolution, Behavior and Systematics ,Dasyurus hallucatus - Abstract
Landscape attributes often shape the spatial genetic structure of species. As the maintenance of genetic connectivity is increasingly a conservation priority, the identification of landscape features that influence connectivity can inform targeted management strategies. The northern quoll (Dasyurus hallucatus) is a carnivorous marsupial that has experienced dramatic population declines in recent decades. To inform management of surviving D. hallucatus populations across north-western Australia we examined the genetic structure of populations, and identified landscape features that influence gene flow within the Kimberley region. We sampled 249 individuals from 28 populations in three regions of north-western Australia, including the Kimberley, Pilbara and Kakadu. Genetic structuring was evident between the three regions and to a lesser extent between the north and central Kimberley. Landscape genetic analysis of Kimberley populations suggest this structuring may be due in part to the indirect effects of differences in rainfall between these two areas. Also, D. hallucatus populations with large areas of open habitat between them tended to be more genetically similar. Managing threats such as the occurrence of intense and frequent fires, and the density of introduced herbivores, could support the persistence of D. hallucatus populations, particularly in areas with high rainfall and flat terrain, where greater genetic connectivity confers a better chance of long-term population survival.
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- 2016
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44. The virtuous circle: predator-friendly farming and ecological restoration in Australia
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Christopher N. Johnson and Arian D. Wallach
- Subjects
0106 biological sciences ,Ecology ,biology ,Natural resource economics ,Human–wildlife conflict ,business.industry ,animal diseases ,010604 marine biology & hydrobiology ,Wildlife ,010603 evolutionary biology ,01 natural sciences ,Virtuous circle and vicious circle ,Agriculture ,biology.animal ,parasitic diseases ,Dingo ,Livestock ,Business ,Trophic cascade ,Restoration ecology ,Ecology, Evolution, Behavior and Systematics ,Nature and Landscape Conservation - Abstract
In Australia, dingoes are widely regarded as enemies of livestock, and accordingly livestock producers commonly attempt to reduce or eradicate them by lethal control. This can have two forms of perverse outcomes: lethal control often does not succeed in reducing dingo populations and can even result in increased attacks on livestock; and the environmental benefits provided by dingoes, some of which are valuable to livestock production, are lost. We describe these outcomes and suggest mechanisms by which tolerance of dingoes could provide benefits to livestock enterprises, at the same time widening the scope of ecological restoration, and humane treatment of wildlife in Australia.
- Published
- 2016
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45. Calculation of Urban Morphology Parameterisations for London for use with the ADMS-Urban Dispersion Model
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Christopher N. Johnson, Mark Jackson, Kate Johnson, and Christina Hood
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Canyon ,geography.geographical_feature_category ,010504 meteorology & atmospheric sciences ,Meteorology ,020209 energy ,Urban morphology ,02 engineering and technology ,Grid cell ,Wind direction ,Python (programming language) ,01 natural sciences ,Urban canopy ,Geography ,0202 electrical engineering, electronic engineering, information engineering ,Air quality index ,computer ,0105 earth and related environmental sciences ,Street canyon ,computer.programming_language - Abstract
Two algorithms have been developed to parameterise the urban morphology of a large urban area, for use with the ADMS-Urban dispersion model. One algorithm calculates parameterisations of the urban canopy, as gridded values of average building height; average street canyon width; ratio of building plan area to grid cell area; and for a user-specified set of wind direction sectors, the ratio of the frontal area of the buildings to grid cell area. The second algorithm calculates parameterisations of the street canyon for individual streets for both sides of the street: canyon height, width, and length. The input data for both algorithms are detailed vector datasets of building and road geometry. The algorithms have been implemented as ArcPy Python tools within ArcGIS. Results are presented for London, calculated for the project Coupled Urban and Regional processes: Effects on AIR quality (CUREAIR). These results used building and road geometry from Ordnance Survey MasterMap Topography.
- Published
- 2016
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46. A triple threat: high population density, high foraging intensity and flexible habitat preferences explain high impact of feral cats on prey
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Christopher N. Johnson, Kirstin M. Proft, Riana Gardiner, Menna E. Jones, and Rowena Hamer
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0106 biological sciences ,animal diseases ,Foraging ,Biodiversity ,Wildlife ,Animals, Wild ,Biology ,010603 evolutionary biology ,01 natural sciences ,General Biochemistry, Genetics and Molecular Biology ,Predation ,Animals ,Quoll ,Ecosystem ,General Environmental Science ,Wildlife conservation ,Population Density ,General Immunology and Microbiology ,Ecology ,010604 marine biology & hydrobiology ,Australia ,Reproducibility of Results ,General Medicine ,biology.organism_classification ,Habitat ,Predatory Behavior ,Cats ,Feral cat ,General Agricultural and Biological Sciences - Abstract
Alien mammalian carnivores have contributed disproportionately to global loss of biodiversity. In Australia, predation by the feral cat and red fox is one of the most significant causes of the decline of native vertebrates. To discover why cats have greater impacts on prey than native predators, we compared the ecology of the feral cat to a marsupial counterpart, the spotted-tailed quoll. Individual prey are 20–200 times more likely to encounter feral cats, because of the combined effects of cats' higher population densities, greater intensity of home-range use and broader habitat preferences. These characteristics also mean that the costs to the prey of adopting anti-predator behaviours against feral cats are likely to be much higher than adopting such behaviours in response to spotted-tailed quolls, due to the reliability and ubiquity of feral cat cues. These results help explain the devastating impacts of cats on wildlife in Australia and other parts of the world.
- Published
- 2021
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47. Conservation trade-offs: Island introduction of a threatened predator suppresses invasive mesopredators but eliminates a seabird colony
- Author
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Vincent P. Scoleri, Menna E. Jones, Peter Vertigan, and Christopher N. Johnson
- Subjects
0106 biological sciences ,biology ,010604 marine biology & hydrobiology ,Puffinus ,Zoology ,15. Life on land ,biology.organism_classification ,010603 evolutionary biology ,01 natural sciences ,Shearwater ,Predation ,Mesopredator release hypothesis ,biology.animal ,Brushtail possum ,Feral cat ,14. Life underwater ,Seabird ,Ecology, Evolution, Behavior and Systematics ,Nature and Landscape Conservation ,Apex predator - Abstract
Offshore islands are ideal for establishing insurance populations of endangered species as they often lack threatening processes found on mainlands. However, introductions of endangered predators can have complex effects on island species. The Tasmanian devil (Sarcophilus harrisii) was introduced to Maria Island in Tasmania, Australia in 2012 to establish an insurance population separate from a novel disease causing declines throughout its native range. Maria Island has small breeding colonies of the short-tailed shearwater (Puffinus tenuirostris) that are preyed on by an invasive mesopredator (feral cat, Felis catus) and an introduced native omnivore (common brushtail possum, Trichosurus vulpecula). We tested whether the introduction of devils increased predation pressure on shearwaters or reduced it by suppressing cat and possum activity. We measured predator activity on shearwater colonies, and surveyed burrow occupancy of shearwater adults and chicks, from 2013 to 2016; we also monitored shearwaters at a colony on a nearby island without terrestrial predators for comparison. Increasing devil activity was associated with decreasing total predator activity at shearwater colonies on Maria Island due to declines in possum and cat activity, evidently caused by predation on possums by devils, and competition with cats. However, shearwater colonies continued to decline, reaching zero occupancy within four years of devil introduction. Because of their larger size and ability to dig, devils had greater impacts on nesting shearwaters than either cats or possums. Conservation translocations of endangered predators must consider trade-offs between their protection and potential impacts on non-threatened native prey species.
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- 2020
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48. Systematic planning can rapidly close the protection gap in Australian mammal havens
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Chris R. Dickman, Christopher N. Johnson, Adrian D. Manning, Peter Copley, Peter Menkhorst, Keith Morris, M. J. Page, Michael Bode, James Q. Radford, John Joseph Kanowski, B. Hill, Russell Palmer, Nicola J. Mitchell, Joss Bentley, Katherine E. Moseby, Sarah Legge, Graeme R. Gillespie, Brendan A. Wintle, Mike Letnic, Jeremy Ringma, Nick Dexter, John C. Z. Woinarski, and Andrew A. Burbidge
- Subjects
0106 biological sciences ,education.field_of_study ,Ecology ,biology ,Vulpes ,010604 marine biology & hydrobiology ,Population ,Introduced species ,15. Life on land ,biology.organism_classification ,010603 evolutionary biology ,01 natural sciences ,Haven ,Fishery ,Geography ,Taxon ,Threatened species ,Mammal ,14. Life underwater ,education ,Protected area ,Ecology, Evolution, Behavior and Systematics ,Nature and Landscape Conservation - Abstract
In the last 30 years, islands and fenced exclosures free of introduced predators (collectively, havens) have become an increasingly used option for protecting Australian mammals imperiled by predation by introduced cats (Felis catus) and foxes (Vulpes vulpes). However, Australia's network of havens is not expanding in a manner that maximizes representation of all predator-susceptible taxa, because of continued emphasis on already-represented taxa. Future additions to the haven network will improve representation of mammals most efficiently if they fill gaps in under-represented predator-susceptible taxa, particularly rodents. A systematic approach to expansion could protect at least one population of every Australian predator-susceptible threatened mammal taxon by the addition of 12 new havens to the current network. Were the current haven network to be doubled in number in a systematic manner, it could protect three populations of every Australian predator-susceptible threatened mammal taxon.
- Published
- 2019
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49. Canine distemper in Nepal's Annapurna Conservation Area - Implications of dog husbandry and human behaviour for wildlife disease
- Author
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Scott Carver, Mukhiya Gotame, Dikpal Krishna Karmacharya, Christopher N. Johnson, Ajay Narsingh Rana, Debby Ng, Saman Man Pradhan, and Dibesh Karmasharya
- Subjects
Male ,0106 biological sciences ,Veterinary medicine ,Physiology ,Parks, Recreational ,viruses ,Carnivora ,Wildlife ,Wildlife disease ,01 natural sciences ,law.invention ,Geographical Locations ,0403 veterinary science ,Seroepidemiologic Studies ,law ,Medicine and Health Sciences ,Prevalence ,Animal Husbandry ,Carnivore ,Distemper Virus, Canine ,Mammals ,Multidisciplinary ,Ecology ,Pets and Companion Animals ,National park ,Eukaryota ,04 agricultural and veterinary sciences ,Carnivory ,Trophic Interactions ,Body Fluids ,Vaccination ,Blood ,Transmission (mechanics) ,Neutering ,Veterinary Diseases ,Community Ecology ,Vertebrates ,Medicine ,Female ,Anatomy ,Research Article ,Asia ,040301 veterinary sciences ,Animal Types ,Science ,Animals, Wild ,Biology ,010603 evolutionary biology ,Dogs ,Nepal ,medicine ,Animals ,Humans ,Domestic Animals ,Distemper ,Behavior ,Canine distemper ,Ecology and Environmental Sciences ,Organisms ,Biology and Life Sciences ,medicine.disease ,Amniotes ,People and Places ,Veterinary Science ,Zoology - Abstract
Dogs are often commensal with human settlements. In areas where settlements are adjacent to wildlife habitat, the management of dogs can affect risk of spillover of disease to wildlife. We assess dog husbandry practices, and measure the prevalence of Canine Distemper Virus (CDV) in dogs, in 10 villages in Nepal's Annapurna Conservation Area (ACA), an important region for Himalayan wildlife. A high proportion (58%) of owned dogs were allowed by their owners to roam freely, and many village dogs originated from urban areas outside the region. CDV antibodies, indicating past exposure, were detected in 70% of dogs, and 13% were positive for P-gene, suggesting current circulation of CDV. This is the first detection of canine distemper virus in a National Park in Nepal Himalaya. Dogs were generally in good condition, and none exhibited clinical signs of CDV infection, which suggests that infections were asymptomatic. CDV exposure varied with village location and age of dogs, but this variation was minor, consistent with high rates of movement of dogs across the region maintaining high seroprevalence. Residents reported the occurrence of several species of wild carnivores in or close to villages. These results suggest a high potential for transmission of CDV from village dogs to wild carnivores in ACA. We suggest that control of dog immigration, along with vaccination and neutering of dogs could mitigate the risk of CDV spillover into wild carnivore populations.
- Published
- 2019
50. State-space modeling reveals habitat perception of a small terrestrial mammal in a fragmented landscape
- Author
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Cesar Peñaherrera-Palma, Menna E. Jones, Vianey Leos-Barajas, Riana Gardiner, Christopher N. Johnson, and Rowena Hamer
- Subjects
0106 biological sciences ,restoration ,Foraging ,Woodland ,Spatial distribution ,010603 evolutionary biology ,01 natural sciences ,03 medical and health sciences ,lcsh:QH540-549.5 ,fragmentation ,Ecology, Evolution, Behavior and Systematics ,Hidden Markov Models ,030304 developmental biology ,Nature and Landscape Conservation ,Original Research ,2. Zero hunger ,0303 health sciences ,Ecology ,fungi ,Fragmentation (computing) ,conservation ,Vegetation ,15. Life on land ,Habitat destruction ,Geography ,Habitat ,Threatened species ,movement ecology ,lcsh:Ecology ,movement ,management - Abstract
Habitat loss is a major cause of species loss and is expected to increase. Loss of habitat is often associated with fragmentation of remaining habitat. Whether species can persist in fragmented landscapes may depend on their movement behavior, which determines their capability to respond flexibility to changes in habitat structure and spatial distribution of patches. Movement is frequently generalized to describe a total area used, or segmented to highlight resource use, often overlooking finer‐scale individual behaviors. We applied hidden Markov models (HMM) to movement data from 26 eastern bettongs (Bettongia gaimardi) in fragmented landscapes. HMMs are able to identify distinct behavior states associated with different movement patterns and discover how these behaviors are associated with habitat features. Three distinct behavior states were identified and interpreted as denning, foraging, and fast‐traveling. The probability of occurrence of each state, and of transitions between them, was predicted by variation in tree‐canopy cover and understorey vegetation density. Denning was associated with woodland with low canopy cover but high vegetation density, foraging with high canopy cover but low vegetation density, and fast‐traveling with low canopy cover and low vegetation density. Bettongs did move outside woodland patches, often fast‐traveling through pasture and using smaller stands of trees as stepping stones between neighboring patches. Males were more likely to fast‐travel and venture outside woodlands patches, while females concentrated their movement within woodland patches. Synthesis and applications: Our work demonstrates the value of using animal movement to understand how animals respond to variation in habitat structure, including fragmentation. Analysis using HMMs was able to characterize distinct habitat types needed for foraging and denning, and identify landscape features that facilitate movement between patches. Future work should extend the use of individual movement analyses to guide management of fragmented habitat in ways that support persistence of species potentially threatened by habitat loss.
- Published
- 2018
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