The evolution of pesticide resistance is a widespread problem with potentially severe consequences for global food security. We introduce the resevol R package, which simulates individual-based ...models of pests with evolving genomes that produce complex, polygenic, and covarying traits affecting pest life history and pesticide resistance. Simulations are modelled on a spatially-explicit and highly customisable landscape in which crop and pesticide application and rotation can vary, making the package a highly flexible tool for both general and tactical models of pest management and resistance evolution. We present the key features of the resevol package and demonstrate its use for a simple example simulating pests with two covarying traits. The resevol R package is open source under GNU Public License. All source code and documentation are available on GitHub.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Environmentally sustainable insect pest control products, such as microbial biopesticides, are increasingly replacing chemical pesticides for crop protection.Most insecticide resistance management ...deals with chemical insecticides and transgenic crops, and was not designed to tackle resistance to microbial biopesticides containing living pathogens.The unique properties of host–parasite interactions offer novel opportunities to proactively manage the risk of pests evolving biopesticide resistance.Genotype-by-environment interactions (GEIs) can have especially large effects on pathogen resistance: resistance allele fitness depends on many aspects of the host environment.By encouraging landscape-wide crop heterogeneity and by diversifying the biopesticides available to farmers, we can exploit GEIs to minimize resistance risks and preserve biopesticide efficacy.
Microbial biopesticides containing living parasites are valuable emerging crop protection technologies against insect pests, but they are vulnerable to resistance evolution. Fortunately, the fitness of alleles that provide resistance, including to parasites used in biopesticides, frequently depends on parasite identity and environmental conditions. This context-specificity suggests a sustainable approach to biopesticide resistance management through landscape diversification. To mitigate resistance risks, we advocate increasing the range of biopesticides available to farmers, whilst simultaneously encouraging other aspects of landscape-wide crop heterogeneity that can generate variable selection on resistance alleles. This approach requires agricultural stakeholders to prioritize diversity as well as efficiency, both within agricultural landscapes and the biocontrol marketplace.
Animal immune systems change dramatically during the ageing process, often accompanied by major increases in pathogen susceptibility. However, the extent to which senescent elevations in infection ...mortality are causally driven by deteriorations in canonical systemic immune processes is unclear. We studied Drosophila melanogaster and compared the relative contributions of impaired systemic immune defences and deteriorating barrier defences to increased pathogen susceptibility in aged flies. To assess senescent changes in systemic immune response efficacy we injected one and four-week old flies with the entomopathogenic fungus Beauveria bassiana and studied subsequent mortality; whereas to include the role of barrier defences we infected flies by dusting the cuticle with fungal spores. We show that the processes underlying pathogen defence senescence differ between males and females. Both sexes became more susceptible to infection as they aged. However, we conclude that for males, this was principally due to deterioration in barrier defences, whereas for females systemic immune defence senescence was mainly responsible. We discuss the potential roles of sex-specific selection on the immune system and behavioural variation between males and females in driving these different senescent trends.
For parasitic platyhelminths that generally lack a fossil record, there is little information on the pathways of morphological change during evolution. Polystomatid monogeneans are notable for their ...evolutionary diversification, having originated from ancestors on fish and radiated in parallel with tetrapod vertebrates over more than 425 million years (My). This study focuses on the genus Polystomoides that occurs almost worldwide on freshwater chelonian reptiles. Morphometric data show a major divergence in structural adaptations for attachment; this correlates with a dichotomy in micro-environmental conditions in habitats within the hosts. Species infecting the urinary tract have attachment organs with large hamuli and small suckers; species in the oro-nasal tract differ fundamentally, having small hamuli and large suckers. Zoogeographical and molecular evidence supports ancient separation of these site-specific clades: a new genus is proposed - Uropolystomoides - containing urinary tract species distinct from Polystomoides sensu stricto in oro-nasal sites. Aside from differences in attachment adaptations, body plans have probably changed little over perhaps 150 My. This case contrasts markedly with polystomatids in other vertebrate groups where major morphological changes have evolved over much shorter timescales; the chelonian parasites show highly stable morphology across their global distribution over a long period of evolution, exemplifying 'living fossils'.
The consequences for wildlife of living in radiologically contaminated environments are uncertain. Previous laboratory studies suggest insects are relatively radiation-resistant; however, some field ...studies from the Chernobyl Exclusion Zone report severe adverse effects at substantially lower radiation dose rates than expected. Here, we present the first laboratory investigation to study how environmentally relevant radiation exposure affects bumblebee life history, assessing the shape of the relationship between radiation exposure and fitness loss. Dose rates comparable to the Chernobyl Exclusion Zone (50-400 µGy h
) impaired bumblebee reproduction and delayed colony growth but did not affect colony weight or longevity. Our best-fitting model for the effect of radiation dose rate on colony queen production had a strongly nonlinear concave relationship: exposure to only 100 µGy h
impaired reproduction by 30-45%, while further dose rate increases caused more modest additional reproductive impairment. Our data indicate that the practice of estimating effects of environmentally relevant low-dose rate exposure by extrapolating from high-dose rates may have considerably underestimated the effects of radiation. If our data can be generalized, they suggest insects suffer significant negative consequences at dose rates previously thought safe; we therefore advocate relevant revisions to the international framework for radiological protection of the environment.
Competition theory states that multiple species should not be able to occupy the same niche indefinitely. Morphologically, similar species are expected to be ecologically alike and exhibit little ...niche differentiation, which makes it difficult to explain the co‐occurrence of cryptic species. Here, we investigated interspecific niche differentiation within a complex of cryptic bumblebee species that co‐occur extensively in the United Kingdom. We compared the interspecific variation along different niche dimensions, to determine how they partition a niche to avoid competitive exclusion. We studied the species B. cryptarum, B. lucorum, and B. magnus at a single location in the northwest of Scotland throughout the flight season. Using mitochondrial DNA for species identification, we investigated differences in phenology, response to weather variables and forage use. We also estimated niche region and niche overlap between different castes of the three species. Our results show varying levels of niche partitioning between the bumblebee species along three niche dimensions. The species had contrasting phenologies: The phenology of B. magnus was delayed relative to the other two species, while B. cryptarum had a relatively extended phenology, with workers and males more common than B. lucorum early and late in the season. We found divergent thermal specialisation: In contrast to B. cryptarum and B. magnus, B. lucorum worker activity was skewed toward warmer, sunnier conditions, leading to interspecific temporal variation. Furthermore, the three species differentially exploited the available forage plants: In particular, unlike the other two species, B. magnus fed predominantly on species of heather. The results suggest that ecological divergence in different niche dimensions and spatio‐temporal heterogeneity in the environment may contribute to the persistence of cryptic species in sympatry. Furthermore, our study suggests that cryptic species provide distinct and unique ecosystem services, demonstrating that morphological similarity does not necessarily equate to ecological equivalence.
We investigated interspecific niche differentiation within a complex of cryptic bumblebee species that co‐occur extensively in the United Kingdom, to determine how they partition a niche to avoid competitive exclusion. Our results show varying levels of niche partitioning between the bumblebee species along three niche dimensions: phenology, response to weather conditions, and forage use. We suggest that these species provide unique ecosystem services and that a combination of ecological divergence in different niche dimensions and spatio‐temporal heterogeneity in the environment may contribute to the persistence of cryptic species in sympatry.
According to Bergmann's rule we expect species with larger body size to inhabit locations with a cooler climate, where they may be well adapted to conserve heat and resist starvation. This rule is ...generally applied to endotherms. In contrast, body size in ectothermic invertebrates has been suggested to follow the reverse ecogeographic trend: these converse Bergmann's patterns may be driven by the ecological constraints of shorter season length and lower food availability in cooler high latitude locations. Such patterns are particularly common in large insects due to their longer development times. As large and facultatively endothermic insects, bumblebees could thus be expected to follow either trend. In this investigation, we studied body size of three bumblebee species over a large spatial area and investigated whether interspecific trends in body size correspond to differences in their distribution consistent with either Bergmann's or a converse Bergmann's rule. We examined the body size of queens, males and workers of the Bombus lucorum complex of cryptic bumblebee species from across the whole of Great Britain. We found interspecific differences in body size corresponding to Bergmann's rule: queens and males of the more northerly distributed, cool-adapted, species were largest. In contrast, the mean body size of the worker caste did not vary between the three species. These differences in body size may have evolved under selection pressures for thermoregulation or starvation resistance. We suggest that this case study in facultatively endothermic insects may help clarify the selection pressures governing Bergmann rule trends more generally.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Viruses are key population regulators, but we have limited knowledge of the diversity and ecology of viruses. This is even the case in wild host populations that provide ecosystem services, where ...small fitness effects may have major ecological impacts in aggregate. One such group of hosts are the bumblebees, which have a major role in the pollination of food crops and have suffered population declines and range contractions in recent decades. In this study, we investigate the diversity of four recently discovered bumblebee viruses (Mayfield virus 1, Mayfield virus 2, River Liunaeg virus, and Loch Morlich virus), and two previously known viruses that infect both wild bumblebees and managed honeybees (Acute bee paralysis virus and Slow bee paralysis virus) from isolates in Scotland. We investigate the ecological and environmental factors that determine viral presence and absence. We show that the recently discovered bumblebee viruses were more genetically diverse than the viruses shared with honeybees. Coinfection is potentially important in shaping prevalence: we found a strong positive association between River Liunaeg virus and Loch Morlich virus presence after controlling for host species, location and other relevant ecological variables. We tested for a relationship between environmental variables (temperature, UV radiation, wind speed, and prevalence), but as we had few sampling sites, and thus low power for site-level analyses, we could not conclude anything regarding these variables. We also describe the relationship between the bumblebee communities at our sampling sites. This study represents a first step in the description of predictors of bumblebee infection in the wild.
Evolutionary ecologists frequently argue that parasite defence is costly because resources must be reallocated from other life‐history traits to fuel the immune response. However, this hypothesis is ...rarely explicitly tested. An alternative possibility is that immune responses impair an organism's ability to acquire the resources it needs to support metabolism. Here, we disentangle these opposing hypotheses for why the activation costs of parasite resistance arise. We studied fecundity costs associated with immune stimulation in Drosophila melanogaster. Then, by measuring correlated changes in metabolic rate, food consumption and body weight, we assessed whether responses were consistent with immunity costs originating from altered resource allocation or from impaired resource acquisition. Microbial injection resulted in a 45% fecundity decrease. It also triggered a mean decline in metabolic rate of 6% and a mean reduction in food intake of 31%; body weight was unaffected. Metabolic rate downregulation was greater in males than in females, whereas declines in food ingestion were of similar magnitude in both sexes. These physiological shifts did not depend on whether microbial challenges were alive or dead, thus they resulted from immune system activation not pathogenesis. These costs of immune activation are significant for individuals that successfully resist infection and might also occur in other situations when immune responses are upregulated without infection. Whilst we found significant activation costs of resistance, our data provide no compelling evidence for the popularly argued hypothesis that immune deployment is costly because of reallocation of energetic resources to the immune system. Instead, reduction in resource acquisition due to ‘infection‐induced anorexia’ may be the principal driver of metabolic changes and fecundity costs resulting from immune response activation.
Exposure to radiation is a natural part of our environment. Yet, due to nuclear accidents such as at Chernobyl, some organisms are exposed to significantly elevated dose rates. Our understanding of ...the effects of radiation in the environment is limited, confounded by substantial interspecific differences in radio‐sensitivity and conflicting findings.
Here we study radiation impacts on bumblebees in the laboratory using principles from life‐history theory, which assume organismal investment in fitness‐related traits is constrained by resource availability and resource allocation decisions. To investigate how chronic radiation might negatively affect life‐history traits, we tested whether exposure affects bumblebee energy budgets by studying resource acquisition (feeding) and resource use (metabolic rate).
We monitored metabolic rate, movement and nectar intake of bumblebees before, during and after 10 days of radiation exposure. Subsequently, we monitored feeding and body mass across a dose rate gradient to investigate the dose rate threshold for these effects. We studied dose rates up to 200 μGy/hr: a range found today in some areas of the Chernobyl Exclusion Zone.
Chronic low‐dose radiation affected bumblebee energy budgets. At 200 μGy/hr nectar consumption elevated by 56% relative to controls, metabolic CO2 production increased by 18%, and time spent active rose by 30%. Once radiation exposure stopped, feeding remained elevated but CO2 production and activity returned to baseline. Our analysis indicates that elevated metabolic rate was not driven by increased activity but was instead closely associated with feeding increases. Our data suggest bumblebee nectar consumption was affected across the 50–200 μGy/hr range.
We show field‐realistic radiation exposure influences fundamental metabolic processes with potential to drive changes in many downstream life‐history traits. We hypothesise that radiation may trigger energetically costly repair mechanisms, increasing metabolic rate and nectar requirements. This change could have significant ecological consequences in contaminated landscapes, including Chernobyl. We demonstrate bumblebees are more sensitive to radiation than assumed by existing international frameworks for environmental radiological protection.
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