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Context: Human disturbance has transformed ecosystems globally, yet studies of the ecological impact of landscape modification are often confounded. Non-random patterns of land clearing cause differing vegetation types and soil productivity between fragments in modified landscapes and reference areas—like national parks—with which they are compared. Objectives: We sought to explore the influence of land modification on herpetofauna and small mammal communities using multiple biodiversity measures—species richness and diversity, individual species abundance, and community composition. We also aimed to investigate the role of traits such as diet, habitat breadth, and litter size in moderating species responses to land modification. Methods: We established 100 sampling sites to survey herpetofauna and small mammals in 11 fragments in an agricultural landscape compared to 11 ecologically equivalent ‘pseudo-fragments’ in a nearby national park in south-eastern Australia. We selected pairs of fragments and pseudo-fragments of the same size and vegetation type, and used identical survey methods to sample pairs simultaneously, thereby controlling for numerous confounding factors, such as differing vegetation type, weather, and survey effort. Results: Species richness and diversity were similar between fragments and pseudo-fragments. Despite this, we found community composition differed markedly—driven by the varying responses of individual species—indicating a shift in fauna communities associated with land modification. Fossorial habit, omnivorous diet, and broad habitat requirements led to higher abundance in fragments whilst arboreality, carnivorous diet, and narrow habitat requirements led to higher abundance in pseudo-fragments. Conclusions: Although fragments hold similar numbers of species to continuous areas, they contain distinct and novel communities, and sustain high abundances of some species. These diverse communities are dominated by native species, including threatened species, and their distinctive composition is shaped by traits conducive to persistence amidst land modification. These novel communities may provide a reservoir of resilience in the face of environmental change and should be viewed as complementary to conservation areas. [ABSTRACT FROM AUTHOR]

Novel interactions between invaders and native species that have evolved in their absence may impose strong selective pressures that drive species to extinction or prompt rapid co-evolution and learning. Here, we report on the effects that invasive cane toads, a toxic prey species, have had on freshwater crocodile populations in 7 waterholes of the Victoria River, Australia, before and up to 14 years after toads invaded. We recorded observations of crocodiles attacking toads, dissected dead crocodiles to determine if they had eaten toads and indexed the abundances of cane toads, live crocodiles and dead crocodiles. Following toad-invasion we observed crocodiles attacking cane toads. Dead crocodiles were only observed following the invasion of toads and 62% of the 71 dead crocodiles we dissected had toads in their stomachs. Counts of dead crocodiles showed a humped relationship with time since toad invasion and declined markedly after 3 years post-toad invasion. Live crocodile abundance declined sharply following toad-invasion, but this decline attenuated approximately 4 years post-invasion. The pulse of crocodile mortality and attenuation of the rate of crocodile population decline suggests that crocodiles have evolved or learned to enable co-existence with toads. However, crocodile populations have shown no sign of recovery in the 8–14 years post toad invasion. Our findings highlight that adaptation by native species to the presence of invaders may be imperfect and thus may not necessarily entail numerical recovery of populations to pre-invasion levels, but instead downward shifts to new equilibria due to ongoing interactions with invaders. [ABSTRACT FROM AUTHOR]

The dispersal tendencies of individuals can provide an important adaptive basis to counter environmental and ecological variation to increase fitness and benefit populations. We evaluated whether indirect genetic-based measures of dispersal of a large monitor lizard (Varanus varius) were sex-biased and further covaried with putative demographic and ecological differences across a forest ecotone in Southern Australia. The mean corrected assignment index (i.e., mAIC) estimated that lace monitors had significant male-biased dispersal. There was strong evidence that common dispersal promoting influences, including lace monitor density and arboreal mammal prey availability, but not the overall male-biased sex ratio, differed with forest type across the ecotone. These different forest types influenced the extent of sex-biased dispersal, with lace monitors captured in banksia woodland having a significant male bias in dispersal, whilst lace monitors sampled in adjacent eucalypt forest showed no difference in assignment values indicating no sex-biased dispersal. However, individual-based spatial autocorrelation analyses and mixed effect models indicated no spatial mediated genetic structuring nor evidence of sex or habitat-related effects. Estimates of recent migration (i.e., < 3 generations) indicated strong and symmetrical migration between banksia woodland and eucalypt forest patches suggesting limited habitat resistance to gene flow across an ecotonal landscape. Not discounting method-specific evidence for male- and forest-type-biased dispersal, the absence of spatial genetic structuring suggests lace monitors retain a high dispersal capacity. An absence of landscape-scale genetic structure is consistent with this species's high vagility. This landscape-scale result is further supported because only the most significant biogeographic barriers (e.g., mountain ranges) impede gene flow within the species' extensive range distribution, allowing for genetic structuring among populations. [ABSTRACT FROM AUTHOR]

Species restricted to archipelagos are often range-restricted, dispersal limited, and persist as disjunct populations. These attributes can make island populations especially vulnerable to extinction from natural or anthropogenic processes. Ascertaining causes of habitat use, population impact, and range loss is fundamental to guiding effective conservation actions. The Komodo dragon (Varanus komodoensis) is an endangered, island-endemic species with a highly restricted range distribution limited to a small number of islands in Eastern Indonesia. Flores Island is the largest island (13,540 km2) within the species distribution. However, with relatively few and small-protected areas, alongside a much higher incidence of human-related habitat use, Komodo dragon habitat occupancy is suspected to decrease on Flores. Here over five years, we conducted systematic surveys to evaluate Komodo dragon habitat occupancy at 346 camera monitoring stations (CMS) distributed along the Flores coastline. We successfully detected Komodo dragons at 85 of the 346 CMS on Flores. The pattern of Komodo dragon site presence indicated their distribution was confined to three isolated and highly restricted habitat areas on the west, northwestern, and northern coastal regions of Flores. Ranking of competing models indicated that proximity to farms and villages had the strongest negative effects on Komodo dragon habitat occupancy. The current predicted Komodo dragon range distribution appeared to have undergone significant range area contraction (~ 44%) at multiple coastal areas known to be occupied by the Komodo dragon detected in previous decades (i.e., 1970–2000). We attribute decreased Komodo dragon habitat use and range loss to multiple and cascading human activities. To address these threats, we advocate a range of land use planning and community conservation actions to avoid a potential Komodo dragon extirpation on the largest island habitat within their distribution. [ABSTRACT FROM AUTHOR]

Animals that face natural and human-mediated landscape disturbance processes can demonstrate different modalities of phenotypic variation to influence local population persistence. Differences in the frequency and pervasiveness of environmental variation can cause an individual's phenotype to demonstrate either directional plasticity (i.e., environmental matching), canalization, or increased trait variance. Furthermore, how important a trait's influence is on fitness can further mediate the nature of phenotypic outcomes to environmental variation. We explored the effects of multi-decadal chronosequences of logging and fire-related forest disturbance on morphological variation of the generalist lizard species, the Yellow-bellied water skink (Eulamprus heatwolei) in Southern Australia. There was evidence that both logging and fire-related disturbance could influence multiple elements of vegetation structure that would construe a major source of environmental variation for lizards. Nevertheless, neither logging nor fire-related disturbance effects resulted in significant differences in lizard morphological traits. However, there was evidence that years post-fire disturbance was associated with a modest but significant increase in a measure of lizard morphological variance. For the most part, we suggest that lizards exhibit canalization in their morphological responses to disturbance related environmental variation. In forests ecosystems with complex temporal and spatial regimes of environmental variation, canalization of lizard morphology could be expected to ensure phenotypic stability within or across generations to favor geometric, over arithmetic, fitness. [ABSTRACT FROM AUTHOR]

The developmental environment an animal experiences can have a pervasive and sustained effect on phenotype throughout its life. Animals exposed to suboptimal conditions during development can experience physiological trade-offs, leading to seemingly negative phenotypic changes in later life that have been hypothesised to have detrimental effects on fitness. However, few studies have investigated how exposure to suboptimal developmental conditions affects an animal's reproductive behavior and fitness. Here, we determine if elevated levels of corticosterone (CORT; the dominant avian stress hormone) during development affect fitness via changes in reproductive investment in adult zebra finches (Taeniopygia guttata). To do this, we exposed nestling zebra finches to either CORT supplemented or control treatments and assessed their mate selection and reproductive investment as adults, using free choice breeding experiments. We found that breeding pairs of birds from matched developmental treatments (CORT or control) had a shorter latency to lay clutches compared to pairs with mismatched developmental treatments. We found no indication that clutch size or egg mass were affected by developmental treatment. Also, we found no evidence that birds choose mates to match their own developmental treatment. Our results demonstrate that developmental experience may affect reproductive investment through changes to reproductive timing and add to the literature suggesting that pairs with similar developmental backgrounds can coordinate their reproduction more effectively. Significance statement: Developmental stress may reduce the fitness of a breeding pair as a result of its detrimental effect on phenotype and performance. Alternatively, individuals could use indicators of developmental stress to influence mate choice in order to compensate for a poor start to life. Previous studies suggest that birds do assortatively mate by developmental environment, but this has not been tested in a free choice mating context. Using a free choice breeding experiment, we show that pairs of breeding birds lay eggs faster when they have matching developmental environments, regardless of the quality of their developmental environment. This evidence suggests that assortatively mated pairs can potentially offset a bad start to life and maintain fitness in spite of the deleterious effects of developmental stress. [ABSTRACT FROM AUTHOR]

Understanding how threatened wildlife can coexist with humans over the long term is a central issue in conservation and wildlife management. Komodo National Park in Eastern Indonesia, harbors the largest extant populations of the endemic Komodo dragon (Varanus komodoensis). Consistent with global trends, this species is expected to be increasingly exposed to human activities and in particular growing ecotourism activities. Here we comprehensively evaluated how human activities affected individual and population level attributes of Komodo dragons. We compared Komodo dragons phenotypic (behaviour, body size, and body condition) and demographic (age structure, sex ratio, survival, and density) responses to variation in human activities across national park. Komodo dragons were found to exhibit pronounced responses to high human activity level relative to sites with low and negligible human activities. Komodo dragons exposed to ecotourism exhibited significantly less wariness, larger body mass, better body condition, and higher survival. These results are entirely consistent with ecotourism activities that provided Komodo dragons with long-term and substantial nutritional subsidies as a consequence of feeding and human food refuse. However, we also noted the potential negative consequences of altered behaviour and adult-biased populations in ecotourism areas which may influence demographic processes through intraspecific competition or predation. To address this issue, we recommend that three management strategies to be implemented in future include: (1) removal of human-mediated nutritional subsidies, (2) alternative ecotourism, and (3) spatial regulation of ecotourism. Furthermore, we advocate the development of approaches to achieve a socio-ecological sustainability that benefits both people and wildlife conservation. [ABSTRACT FROM AUTHOR]

Understanding the impacts that invasive vertebrates have on terrestrial ecosystems extends primarily to invaders’ impacts on species with which they interact directly through mechanisms such as predation, competition and habitat modification. In addition to direct effects, invaders can also initiate ecological cascades via indirect population level effects on species with which they do not directly interact. However, evidence that invasive vertebrates initiate ecological cascades in terrestrial ecosystems remains scarce. Here, we ask whether the invasion of the cane toad, a vertebrate invader that is toxic to many of Australia’s vertebrate predators, has induced ecological cascades in a semi-arid rangeland. We compared activity of a large predatory lizard, the sand-goanna, and abundances of smaller lizards preyed upon by goannas in areas of high toad activity near toads’ dry season refuges and areas of low toad activity distant from toads’ dry season refuges. Consistent with the hypothesis that toad invasion has led to declines of native predators susceptible to poisoning, goanna activity was lower in areas of high toad activity. Consistent with the hypothesis that toad-induced goanna decline lead to increases in abundance the prey of goannas, smaller lizards were more abundant in areas of high toad activity. Structural equation modelling showed a positive correlation between goanna activity and distance from dry season refuge habitats used by toads. The abundances of small lizards was correlated negatively with goanna activity and distance from dry season refuges of toads. Our findings provide support for the notion that invasions by terrestrial vertebrates can trigger ecological cascades. [ABSTRACT FROM AUTHOR]

In some species, females develop bright colouration to signal reproductive status and exhibit behavioural repertoires to incite male courtship and/or reduce male harassment and forced copulation. Sex steroids, including progesterone and testosterone, potentially mediate female reproductive colouration and reproductive behaviour. We measured associations among plasma profiles of testosterone and progesterone with variation in colour expression and reproductive behaviour, including unique courtship rejection behaviours, in female Lake Eyre dragon lizards, ( Ctenophorus maculosus). At onset of breeding, progesterone and testosterone increased with vitellogenesis, coincident with colour intensification and sexual receptivity, indicated by acceptance of copulations. As steroid levels peaked around the inferred ovulation time, maximal colour development occurred and sexual receptivity declined. When females were gravid and exhibited maximal mate rejection behaviours, progesterone levels remained consistently high, while testosterone exhibited a discrete second peak. At oviposition, significant declines in plasma steroid levels, fading of colouration and a dramatic decrease in male rejection behaviours co-occurred. Our results indicate a generally concordant association among steroid levels, colouration, behaviour and reproductive events. However, the prolonged elevation in progesterone and a second peak of testosterone was unrelated to reproductive state or further colour change, possibly suggesting selection on females to retain high steroid levels for inducing rejection behaviours. [ABSTRACT FROM AUTHOR]

Variation in environmental conditions at a foraging area or at a nesting rookery has the potential to impact reproductive output of green sea turtles (Chelonia mydas) by affecting food resources or the nesting substrate. In this paper we test whether turtles‘ physiological characteristics reflect variation in relevant environmental conditions. We did this by profiling metabolic and hormonal markers among (1) non-vitellogenic females from three different foraging areas and (2) nesting females from different rookeries and breeding seasons. Among the non-vitellogenic females, the highest plasma triglyceride concentrations (4.29 mmol/l) and the lowest plasma cholesterol concentrations (1.27 mmol/l) were found in non-vitellogenic females residing in Moreton Bay during the El Niño year of 1997. Furthermore, during 1997, these Moreton Bay females had higher plasma triglyceride and lower cholesterol concentrations than those recorded in non-vitellogenic females foraging at Heron Reef (triglyceride 1.22 mmol/l and cholesterol 4.53 mmol/l) and Shoalwater Bay (triglyceride 1.69 mmol/l and cholesterol 3.50 mmol/l) in the same year. Among nesting turtles, those nesting at Raine Island had low mean plasma triglyceride concentrations during the high density 1996 nesting season. For those nesting at Heron Island, the mean triglyceride concentrations were the lowest during the 1997 nesting season. This is the first time that hormone and metabolic markers have been used in concert to compare the physiological condition of nesting and foraging sea turtles and its relationship with the environment. Collectively, our data indicate that variation in the environmental conditions at both foraging and nesting areas are reflected at a physiological level. Moreover, our study indicates that turtles feeding during El Niño years are able to attain higher levels of body condition, and that physiological data combined with morphometric data is a useful proxy for assessing the condition of turtles in foraging areas. [ABSTRACT FROM AUTHOR]

Monitor lizards are unique among ectothermic reptiles in that they have high aerobic capacity and distinctive cardiovascular physiology resembling that of endothermic mammals. Here, we sequence the genome of the Komodo dragon Varanus komodoensis, the largest extant monitor lizard, and generate a high-resolution de novo chromosome-assigned genome assembly for V. komodoensis using a hybrid approach of long-range sequencing and single-molecule optical mapping. Comparing the genome of V. komodoensis with those of related species, we find evidence of positive selection in pathways related to energy metabolism, cardiovascular homoeostasis, and haemostasis. We also show species-specific expansions of a chemoreceptor gene family related to pheromone and kairomone sensing in V. komodoensis and other lizard lineages. Together, these evolutionary signatures of adaptation reveal the genetic underpinnings of the unique Komodo dragon sensory and cardiovascular systems, and suggest that selective pressure altered haemostasis genes to help Komodo dragons evade the anticoagulant effects of their own saliva. The Komodo dragon genome is an important resource for understanding the biology of monitor lizards and reptiles worldwide.