Search

When plants establish outside their native range, their ability to adapt to the new environment is influenced by both demography and dispersal. However, the relative importance of these two factors is poorly understood. To quantify the influence of demography and dispersal on patterns of genetic diversity underlying adaptation, we used data from a globally distributed demographic research network comprising 35 native and 18 nonnative populations of Plantago lanceolata Species-specific simulation experiments showed that dispersal would dilute demographic influences on genetic diversity at local scales. Populations in the native European range had strong spatial genetic structure associated with geographic distance and precipitation seasonality. In contrast, nonnative populations had weaker spatial genetic structure that was not associated with environmental gradients but with higher within-population genetic diversity. Our findings show that dispersal caused by repeated, long-distance, human-mediated introductions has allowed invasive plant populations to overcome environmental constraints on genetic diversity, even without strong demographic changes. The impact of invasive plants may, therefore, increase with repeated introductions, highlighting the need to constrain future introductions of species even if they already exist in an area.

Identifying and understanding status and trends in ecological indicators motivates continual monitoring over decades. Many programs rely on probability surveys and their companion design‐based estimators for status assessments (e.g. Horvitz–Thompson). Design‐based estimators do not easily extend to trend estimation nor situations with observation errors. Field‐based monitoring efforts inevitably have turnover of field crew members which may affect consistency and accuracy of data collection over time. Additionally, design‐based estimators ignore the complexities of spatial and temporal heterogeneity in an ecological indicator and how this variability may be linked to environmental or biological dynamics. We propose monitoring programs should re‐evaluate their prescribed statistical methods, consider model‐based approaches and adapt their sampling designs as needed to improve inferences.The Greater Yellowstone Ecosystem, home to two of the most iconic U.S. National Parks, has experienced significant declines in whitebark pine Pinus albicaulis communities due to forest pathogens, insect outbreaks, wildland fires and drought. Whitebark pine is a keystone species found in mountainous environments throughout the Western U.S. and Canada. We assessed the design‐based ratio estimator originally recommended for estimating prevalence of white pine blister rust Cronartium ribicola. We compared the design‐based estimator to a model‐based approach that accounts for the sampling design, imperfect detection and allows for infection probabilities to vary over space and time.Ignoring observation errors led to lower estimated prevalence of white pine blister rust in the general population. Using model‐based approaches, we found that the probability of infection has increased since 2004. However, overall prevalence likely has not changed because of the mountain pine beetle Dendroctonus ponderosae‐induced shift towards smaller diameter trees that have a lower probability of infection compared to their larger cohorts.Synthesis and Applications. Using a design‐based approach to detect change in ecological indicators falls short because of the inability to account for observation errors or to explore environmental or biological factors explaining temporal dynamics. Inherently understanding the mechanisms leading to changes in an ecological indicator over time informs potential management actions. Our assessment underscores the need for continued evaluation and updating of a monitoring program's sampling design and analytical procedures to maintain relevancy. [ABSTRACT FROM AUTHOR]

Predicting biological invasions remains a challenge to applied ecologists and limits pre‐emptive management of biosecurity threats. In the last decade, spotted‐wing drosophila Drosophila suzukii has emerged as an internationally significant agricultural pest as it rapidly spread across Europe and the Americas. However, the underlying drivers of its global invasion remain unstudied, while countries like Australia, presently free from D. suzukii, require robust estimates of spread and establishment potential to aid development of effective preparedness strategies.Here, we analysed the ecoclimatic and human‐mediated drivers of the global invasion of D. suzukii to understand historical spread patterns and improve forecasts of future spread potential. Using a modular approach, climate‐driven population dynamics were linked in space via dispersal processes to simulate spread at continental scales. Combined with biological parameters measured in laboratory studies, the spread model was parameterized and validated on international spread data.Model accuracy was high and was able to predict 83% of regional presence–absence through time in the United States and, without further model fitting, 78% of the variation in the Europe incursion. Omitting human‐assisted spread from the model reduced predictability by over 20%, highlighting the large anthropogenic influence in this modern biological invasion. Economic activity (GDP) rather than human population density was more strongly associated with human‐mediated spread. Simulations predicted that eastern Australian coastal regions, particularly those near major cities with high economic activity, will result in the fastest spread of D. suzukii.Synthesis and applications. Incursions of Drosophila suzukii into Australia will have significant consequences for horticultural industries with the predicted speed of spread making eradication programs extremely difficult. However, the identified areas of significant fruit production, and high environmental suitability and economic activity will form a logical means for prioritizing industry preparedness. In light of our findings, a key component of preparedness strategies will be the ability of fruit producers to rapidly transition to effective management of D. suzukii. [ABSTRACT FROM AUTHOR]

Gut microbiome disequilibrium is increasingly implicated in host fitness reductions, including for the economically important and disease‐challenged western honey bee Apis mellifera. In laboratory experiments, the antibiotic tetracycline, which is used to prevent American Foulbrood Disease in countries including the US, elevates honey bee mortality by disturbing the microbiome. It is unclear, however, how elevated individual mortality affects colony‐level fitness.We used an agent‐based model (BEEHAVE) and empirical data to assess colony‐level effects of antibiotic‐induced worker bee mortality, by measuring colony size. We investigated the relationship between the duration that the antibiotic‐induced mortality probability is imposed for and colony size.We found that when simulating antibiotic‐induced mortality of worker bees from just 60 days per year, up to a permanent effect, the colony is reduced such that tetracycline treatment would not meet the European Food Safety Authority's (EFSA) honey bee protection goals. When antibiotic mortality was imposed for the hypothetical minimal exposure time, which assumes that antibiotics only impact the bee's fitness during the recommended treatment period of 15 days in both spring and autumn, the colony fitness reduction was only marginally under the EFSA's threshold.Synthesis and Applications. Modelling colony‐level impacts of antibiotic treatment shows that individual honey bee worker mortality can lead to colony mortality. To assess the full impact, the persistence of antibiotic‐induced mortality in honey bees must be determined experimentally, in vivo. We caution that as the domestication of new insect species increases, maintaining healthy gut microbiomes is of paramount importance to insect health and commercial productivity. The recommendation from this work is to limit prophylactic use of antibiotics and to not exceed recommended treatment strategies for domesticated insects. This is especially important for highly social insects as excess antibiotic use will likely decrease colony growth and an increase in colony mortality. [ABSTRACT FROM AUTHOR]

The global spread of invasive plant pathogens is increasing, putting natural forests and ecosystem services under threat. Spatial data can quantify range non‐overlap between invasive pathogens and their hosts to identify existing and potentially restorable refugia to enable 'escape' from the pathogen.In 2017, myrtle rust Austropuccinia psidii was detected in New Zealand. New Zealand has 27 native woody and liana species in the plant family susceptible to the disease (Myrtaceae), many of which are ecosystem dominants and economically important. Spatial methods were used to compare the current New Zealand distribution of myrtle rust with the modelled distributions of its potential native hosts. To guide management and set priorities for conservation of at‐risk species, areas of potential refugia where a Myrtaceae species is predicted to occur outside the pathogen range were identified under two myrtle rust distribution scenarios.Myrtle rust will thrive in New Zealand's warmer regions. Many native Myrtaceae are distributed within this area, but several species occur extensively outside the core range of the disease. Species distributed in cooler southern regions will be best placed to persist in refugia.Myrtaceae species with specific habitat requirements and narrow geographical ranges in warmer (northern) areas are likely to require ex situ or active in situ management. Even widely distributed species will benefit from the restoration of suitable habitat that supports multiple species outside the myrtle rust range.Synthesis and applications. Spatial data can be used to identify refugia and restoration opportunities, and thus inform landscape‐level management responses to invasive pathogens. This approach can guide decisions over where to implement in situ (e.g. fungicide spraying) versus ex situ (e.g. seed banking, botanic gardens) management efforts. [ABSTRACT FROM AUTHOR]

The development of genetically modified (GM) mosquitoes and their subsequent field release offers innovative and cost‐effective approaches to reduce mosquito‐borne diseases, such as malaria. A sex‐distorting autosomal transgene has been developed recently in G3 mosquitoes, a laboratory strain of the malaria vector Anopheles gambiae s.l. The transgene expresses an endonuclease called I‐PpoI during spermatogenesis, which selectively cleaves the X chromosome to result in ~95% male progeny. Following the World Health Organization guidance framework for the testing of GM mosquitoes, we assessed the dynamics of this transgene in large cages using a joint experimental modelling approach.We performed a 4‐month experiment in large, indoor cages to study the population genetics of the transgene. The cages were set up to mimic a simple tropical environment with a diurnal light‐cycle, constant temperature and constant humidity. We allowed the generations to overlap to engender a stable age structure in the populations. We constructed a model to mimic the experiments, and used the experimental data to infer the key model parameters.We identified two fitness costs associated with the transgene. First, transgenic adult males have reduced fertility and, second, their female progeny have reduced pupal survival rates. Our results demonstrate that the transgene is likely to disappear in <3 years under our confined conditions. Model predictions suggest this will be true over a wide range of background population sizes and transgene introduction rates.Synthesis and applications. Our study is in line with the World Health Organization guidance recommendations in regard to the development and testing of GM mosquitoes. Since the transgenic sex ratio distorter strain (Ag(PMB)1) has been considered for genetic vector control of malaria, we recorded the dynamics of this transgene in indoor‐large cage populations and modelled its post‐release persistence under different scenarios. We provide a demonstration of the self‐limiting nature of the transgene, and identified new fitness costs that will further reduce the longevity of the transgene after its release. Finally, our study has showcased an alternative and effective statistical method for characterizing the phenotypic expression of a transgene in an insect pest population. [ABSTRACT FROM AUTHOR]

Supplemental feeding can increase the overall health of animals but also can have varying consequences for animals dealing with parasites. Furthermore, the mechanism mediating the effect of food supplementation on host–parasite interactions remains poorly understood.The goal of the study was to determine the effect of food supplementation on host defences against parasitic nest flies and whether host gut microbiota, which can affect immunity, potentially mediates these relationships. In a fully crossed design, I experimentally manipulated the abundance of parasitic nest flies Protocalliphora sialia and food availability then characterized the gut microbiota, immune responses and nest parasite abundance of nestling eastern bluebirds Sialia sialis.Food supplemented birds had 75% fewer parasites than unsupplemented birds. Parasite abundance decreased throughout the breeding season for unsupplemented birds, but abundance did not change throughout the season for supplemented birds.Food supplementation increased overall fledging success. Parasitism had a sublethal effect on blood loss, but food supplementation mitigated these effects by increasing parasite resistance via the nestling IgY antibody response.Food supplementation increased the gut bacterial diversity in nestlings, which was negatively related to parasite abundance. Food supplementation also increased the relative abundance of Clostridium spp. in nestlings, which was positively related to their antibody response and negatively related to parasite abundance.Synthesis and applications. Overall, the results of this study suggest that food supplementation, especially early in the breeding season, increases resistance to parasitism during the early life stage of the host, which might be mediated by the gut microbiota. Wildlife food supplementation is a common pastime for humans worldwide and therefore it is important to understand the consequences of this activity on animal health. Furthermore, supplemental feeding could induce resistance to detrimental parasites (e.g. invasive parasites) in hosts when management of the parasite is not immediately possible. [ABSTRACT FROM AUTHOR]

A promising strategy for reducing the transmission of dengue and other arboviral human diseases by Aedes aegypti mosquito vector populations involves field introductions of the endosymbiotic bacteria Wolbachia. Wolbachia infections inhibit viral transmission by the mosquito, and can spread between mosquito hosts to reach high frequencies in the vector population. Wolbachia spreads by maternal transmission, and spread dynamics can be variable and highly dependent on natural mosquito population dynamics, population structure and fitness components.We develop a mathematical model of an A. aegypti metapopulation that incorporates empirically validated relationships describing density‐dependent mosquito fitness components. We assume that density dependent relationships differ across subpopulations, and construct heterogeneous landscapes for which model‐predicted patterns of variation in mosquito abundance and demography approximate those observed in field populations. We then simulate Wolbachia release strategies similar to that used in field trials.We show that our model can produce rates of spatial spread of Wolbachia similar to those observed following field releases.We then investigate how different types of spatio‐temporal variation in mosquito habitat, as well as different fitness costs incurred by Wolbachia on the mosquito host, influence predicted spread rates. We find that fitness costs reduce spread rates more strongly when the habitat landscape varies temporally due to stochastic and seasonal processes.Synthesis and applications: Our empirically based modelling approach represents effects of environmental heterogeneity on the spatial spread of Wolbachia. The models can assist in interpreting observed spread patterns following field releases and in designing suitable release strategies for targeting spatially heterogeneous vector populations. Our empirically based modelling approach represents effects of environmental heterogeneity on the spatial spread of Wolbachia. The models can assist in interpreting observed spread patterns following field releases and in designing suitable release strategies for targeting spatially heterogeneous vector populations. [ABSTRACT FROM AUTHOR]

Farmland biodiversity benefits pollination, biological control and other key ecosystem services. Food safety has been seen as an exception to this broader pattern, as diverse farmlands attract wildlife that vector foodborne human pathogens. Resulting mitigation efforts thus often seek to deter wildlife by removing natural habitats, while also excluding vertebrate livestock. However, surprising recent evidence suggests that farm simplification actually increases the likelihood that produce will be contaminated with human pathogens.Here, we consider the possibility that intensified agriculture harms faeces‐feeding (coprophagous) beetles and bacteria, which could contribute to heightened food‐safety risk. In 70 commercial vegetable fields spanning the US west coast, using either organic or conventional farming methods, we surveyed coprophages both above‐ and below‐ground. We also measured removal rates of the faeces of Sus scrofa, which vectors foodborne pathogens both as livestock and as feral wildlife.Above‐ground, organic farms fostered dung beetle species that removed S. scrofa faeces more rapidly than was seen on conventional farms, although this benefit was weakened in simplified landscapes dominated by pasture and an introduced dung beetle. Below‐ground, organic farming encouraged significantly higher biodiversity among soil bacteria. Organic farming similarly benefitted dung beetles and bacteria on farms that produced livestock alongside vegetables, or vegetables alone.Complementary laboratory experiments revealed that the dung beetle species and biodiverse bacterial assemblages typical of organic farms were significantly more effective at suppressing human‐pathogenic Escherichia coli O157:H7, compared to coprophage communities associated with conventional farms. This suggests that farm management practices, coprophage conservation, and human–pathogen suppression might be linked.Synthesis and applications. Altogether, our results indicate that insects and microbes can rapidly remove faeces, with the potential to also decrease the persistence of human pathogens. In turn, this suggests that improved food safety may be an important, and perhaps underappreciated, ecosystem service that is enhanced by on‐farm biodiversity. We recommend that farm managers and regulators consider the risks and benefits to coprophages when making management decisions regarding food safety. Altogether, our results indicate that insects and microbes can rapidly remove faeces, with the potential to also decrease the persistence of human pathogens. In turn, this suggests that improved food safety may be an important, and perhaps underappreciated, ecosystem service that is enhanced by on‐farm biodiversity. We recommend that farm managers and regulators consider the risks and benefits to coprophages when making management decisions regarding food safety. Editor's Choice [ABSTRACT FROM AUTHOR]

Conservation biological control aims to control pests by promoting wild populations of natural enemies. One challenge is to attract and retain efficient natural enemies in crop fields, which often are a suboptimal environment. Towards this goal, the attract‐and‐reward strategy relies on combining attractive synthetically produced herbivore‐induced plant volatiles (HIPVs) with companion plants (non‐crop plants which provide alternative resources to the targeted natural enemies). Although severely overlooked, the spatial arrangement of HIPV dispensers and rewards inside crop fields may strongly influence the foraging behaviour and persistence of natural enemies and thus the success of this pest management strategy.We tested the impact of two contrasting spatial arrangements of HIPV dispensers and rewards, alternatively inside and around a block of target apple trees, on the efficacy of the biological control of Aphis citricola populations by the common predatory ladybird Propylea japonica in apple orchards in northern China. We used synthetic methyl salicylate (MeSA) as an attractant and the companion plant Calendula officinalis as a reward. To better understand how the spatial arrangement of MeSA dispensers and companion plants affected the attraction and foraging behaviour of adult ladybirds, we conducted indoor experiments in a flight mill, an olfactometer and a wind‐tunnel.Blocks of target trees treated with MeSA dispensers inside and companion plants around provided the most efficient pest control in orchards, compared with the opposite spatial arrangement.The synthetic MeSA dispenser and the companion plant synergistically attracted ladybirds in the olfactometer and enhanced their flight activity in the flight mill. In the wind‐tunnel, MeSA served as a spatial cue for ladybirds to find nearby prey, while companion plants were sought in the absence of prey.Synthesis and applications. This study aims to further improve aphid control in apple orchards through a careful spatial arrangement of herbivore‐induced plant volatiles dispensers (HIPVs) and rewards (companion plants) in optimized attract‐and‐reward strategies. Without such assessment, these strategies may be hazardous even with well‐identified targeted natural enemies. Associated lab experiments highlight that interactions between HIPVs and companion plants influence ladybird foraging pattern, and that their spatial arrangement can modulate the ability of such key predators to find their prey. This study aims to further improve aphid control in apple orchards through a careful spatial arrangement of herbivore‐induced plant volatiles dispensers (HIPVs) and rewards (companion plants) in optimized attract‐and‐reward strategies. Without such assessment, these strategies may be hazardous even with well‐identified targeted natural enemies. Associated lab experiments highlight that interactions between HIPVs and companion plants influence ladybird foraging pattern, and that their spatial arrangement can modulate the ability of such key predators to find their prey. [ABSTRACT FROM AUTHOR]