Prey Traits Research Articles

Learning to Hunt on the Go: Dietary Changes During Development of Rhinolophid Bats.

Mammals may experience physical changes from birth, and their diet varies at different stages of life. This study investigates the impact of development on the diet composition of three horseshoe bats: Rhinolophus euryale, R. hipposideros, and R. ferrumequinum in the Basque Country, north of the Iberian Peninsula. The diets of juvenile and adult individuals of each species were obtained by analysing their droppings using metabarcoding and then compared at (1) the taxonomic and (2) prey trait levels (size, flying speed, hardness). The diets of juvenile and adult individuals of R. euryale and R. hipposideros showed significant differences at the taxonomic level and regarding prey traits. In contrast, in the case of R. ferrumequinum, we could only observe discernible diet patterns through the trait analysis. Additionally, we discovered a shared pattern: younger individuals tend to feed on easier-to-hunt and/or handle smaller and smoother prey. The varying degrees of dissimilarity between juvenile and adult diets observed in this study suggest that the relative importance of psychomotor development, foraging strategies, prey discrimination, and/or spatial learning may differ among species. These findings contribute to conservation efforts, especially by recognising the dietary needs of juveniles for their survival and successful development.

Heritable intraspecific variation among prey in size and movement interact to shape predation risk and potential natural selection

Abstract Predator and prey traits are important determinants of the outcomes of trophic interactions. In turn, the outcomes of trophic interactions shape predator and prey trait evolution. How species' traits respond to selection from trophic interactions depends crucially on whether and how heritable species' traits are and their genetic correlations. Of the many traits influencing the outcomes of trophic interactions, body size and movement traits have emerged as key traits. Yet, how these traits shape and are shaped by trophic interactions is unclear, as few studies have simultaneously measured the impacts of these traits on the outcomes of trophic interactions, their heritability, and their correlations within the same system. We used outcrossed lines of the ciliate protist Paramecium caudatum from natural populations to examine variation in morphology and movement behaviour, the heritability of that variation, and its effects on Paramecium susceptibility to predation by the copepod Macrocyclops albidus. We found that the Paramecium lines exhibited heritable variation in body size and movement traits. In contrast to expectations from allometric relationships, body size and movement speed showed little covariance among clonal lines. The proportion of Paramecium consumed by copepods was positively associated with Paramecium body size and velocity but with an interaction such that greater velocities led to greater predation risk for large body‐sized paramecia but did not alter predation risk for smaller paramecia. The proportion of paramecia consumed was not related to copepod body size. These patterns of predation risk and heritable trait variation in paramecia suggest that copepod predation may act as a selective force operating independently on movement and body size and generating the strongest selection against large, high‐velocity paramecia. Our results illustrate how ecology and genetics can shape potential natural selection on prey traits through the outcomes of trophic interactions. Further simultaneous measures of predation outcomes, traits, and their quantitative genetics will provide insights into the evolutionary ecology of species interactions and their eco‐evolutionary consequences. Read the free Plain Language Summary for this article on the Journal blog.

Integrating eDNA metabarcoding and citizen science enhances avian ecological research.

Research Highlight: Bourbour etal., 2024. Feeding en route: Prey availability and traits influence prey selection by an avian predator on migration. Journal of Animal Ecology. Diet selection plays a key role in the eco-evolutionary dynamics of animals, exhibiting substantial variability across species, environments and seasons. The complex interplay between movement capability, hunting strategies, habitat use, prey traits and availability shapes the foraging patterns of avian predators. However, detailed information on how these birds exploit their extensive territories remains limited. In this study, Bourbour etal. utilised a novel integration of eDNA metabarcoding and citizen science to explore predator-prey interactions between migrating sharp-shinned hawks (Accipiter striatus) and an ephemeral avian prey community along North America's Pacific flyway. The research identified 1396 detections from the diet (65 species) of 588 migrating sharp-shinned hawks. Hawks' diet composition correlated with prey abundance indices sourced from the eBird database throughout the migration season, highlighting the significant impact of prey availability-shaped by migration tendency, flocking behaviour, and habitat-on raptor-songbird interactions. Notably, the study also found significant differences in prey size between male and female hawks, indicating that sexual dimorphism has led to diverse foraging strategies during migration. These findings underscore the potential of combining eDNA metabarcoding with citizen science to deepen our understanding of the foraging ecology of highly mobile and wide-ranging birds, as well as to monitor complex and vast ecosystems.

Predator-prey trait associations and feeding preferences of demersal fishes in the southern North Sea

In marine ecosystems under ongoing long-term changes, reducing complex food webs to their functionally important properties enables systematic analysis of bottom-up/top-down regulations and species turnover. The assessment of feeding interactions in the form of predator and prey trait associations provides a better understanding of predators’ criteria for prey selection and thus is a promising approach to reduce complexity. Here, we tested RLQ ordination and fourth-corner analysis, complementary multivariate approaches, as tools to identify ecologically relevant associations between the traits of 8 demersal fish species in the southern North Sea and their fish or benthic prey. To scrutinize the trait-based results in their appropriateness to reflect selective feeding behaviour of the predator species, we compared them with a taxon-based electivity index, Chesson’s α. Among 7 predator traits investigated, body tissue composition represented by omega-3 polyunsaturated fatty acid content was significantly associated with prey traits, being positively correlated with energy density of the prey and negatively with prey of low mobility. Comparisons with the electivity indices showed that the prey preferred by predators corresponded relatively well with the identified prey trait preferences. The results of the tested analysis approach support its use when assessing the mutual dependences of predator and prey populations on a functional level. Provided the data availability and quality of feeding-related traits is sufficiently high, trait-based predator-prey analysis with RLQ and fourth-corner analyses offers new possibilities for understanding food web dynamics in the context of climate-change-induced species distribution shifts.

Feeding en route: Prey availability and traits influence prey selection by an avian predator on migration.

During animal migration, ephemeral communities of taxa at all trophic levels co-occur over space and time. The interactions between predators and prey along migration corridors are ecologically and evolutionarily significant. However, these interactions remain understudied in terrestrial systems and warrant further investigations using novel approaches. We investigated the predator-prey interactions between a migrating avivorous predator and ephemeral avian prey community in the fall migration season. We tested for associations between avian traits and prey selection and hypothesized that prey traits (i.e. relative size, flocking behaviour, habitat, migration tendency and availability) would influence prey selection by a sexually dimorphic raptor on migration. To document prey consumption, we sampled trace prey DNA from beaks and talons of migrating sharp-shinned hawks Accipiter striatus (n = 588). We determined prey availability in the ephemeral avian community by extracting weekly abundance indices from eBird Status and Trends data. We used discrete choice models to assess prey selection and visualized the frequency of prey in diet and availability on the landscape over the fall migration season. Using eDNA metabarcoding, we detected prey species on 94.1% of the hawks sampled (n = 525/588) comprising 1396 prey species detections from 65 prey species. Prey frequency in diet and eBird relative abundance of prey species were correlated over the migration season for top-selected prey species, suggesting prey availability is an important component of raptor-songbird interactions during fall. Prey size, flocking behaviour and non-breeding habitat association were prey traits that significantly influenced predator choice. We found differences between female and male hawk prey selection, suggesting that sexual size dimorphism has led to distinct foraging strategies on migration. This research integrated field data collected by a volunteer-powered raptor migration monitoring station and public-generated data from eBird to reveal elusive predator-prey dynamics occurring in an ephemeral raptor-songbird community during fall migration. Understanding dynamic raptor-songbird interactions along migration routes remains a relatively unexplored frontier in animal ecology and is necessary for the conservation and management efforts of migratory and resident communities.

Better to bluff than run: conservation implications of feral-cat prey selectivity

Context Predators typically select prey on the basis of their availability and traits such as body size, speed, camouflage and behaviour that influence ease of capture. Such selectivity, particularly by invasive predators, can disproportionately affect the conservation status of prey. Control of top-order predators can also trigger trophic cascades if subordinate predators have different prey preference. Aims We aimed to document prey selectivity of feral cats by comparing their diet with prey availability over a 27-year study in an Australian desert. Methods Stomach-content and demographic data were recorded from 2293 feral cats, showing 3939 vertebrate prey. These were compared with vertebrate-prey availability estimated from 224,472 pitfall-trap nights, 9791 Elliott-trap nights and opportunistic sampling that accumulated 9247 small mammal and 32,053 herptile records. Potential bird availability was assessed through 2072 quantitative counts amounting to 29,832 bird records. We compared cat selectivity among species, guilds, and physical and behavioural traits of potential prey. Key results Prey guild selectivity from two quantitative subsets of these data indicated that cats preferentially selected medium-sized rodents, snakes and ground-nesting birds over other prey guilds, and also preyed extensively on rabbits, for which selectivity could not be assessed. Species that froze or responded defensively to predators were less favoured than were prey that fled, including fast-evading species. Species inhabiting dunes were hunted more frequently relative to their abundance than were closely related species on stony plains. Conclusions The size, habitat preference and response to predators of potential prey species affect their targeting by feral cats. Implications Our results assist assessment of risk to wildlife species from cat predation and suggest that cat control will trigger changes in the relative abundance of prey species depending on their size, habitat use and behaviour.

Functional traits of predators and decomposer prey determine context dependency in trophic control over ecosystems.

Research Highlight: Piccoli, G. C. d. O., Antiqueira, P. A. P., Srivastava, D. S., & Romero, G. Q. (2024). Trophic cascades within and across ecosystems: The role of anti-predatory defences, predator type and detritus quality. Journal of Animal Ecology, 00, 1-14. https://doi.org/10.1111/1365-2656.14063. Ecosystem functioning is controlled by the interplay between bottom-up supply of limiting nutrients and top-down animal feedback effects. However, the degree of animal versus nutrient control is context-dependent. A key challenge lies in characterizing this context dependency which is hypothesized to depend on differences in animal functional traits. Reporting on an important experiment, Piccoli etal. (2014) evaluate how interactions among functionally different predators and decomposer prey create context dependency in top-down control of a model system-tropical bromeliad tank ecosystems. Bromeliad plants hold water in their tanks supporting microcosm ecosystems containing terrestrial and aquatic insect larvae and arachnids. The ecosystems are supported by nutrients in plant litter that rains down from forest canopies into the tanks. Nutrients are released after litter is decomposed by a functionally diverse community of larval insect decomposers that differ in feeding mode and antipredator defence strategy. This decomposer community is preyed upon by an exclusively narrowly ranging aquatic insect larval predator and widely ranging spider predator that crosses between the aquatic and surrounding terrestrial ecosystems. Experimental manipulation of the animal community to test for the degree of control by predators mediated by the functionally diverse prey community included four treatments: (i) a control with the detritivores composing different function groups but without predators, (ii) the cross-ecosystem spider predator added, (iii) the purely aquatic damselfly larvae predator added and (iv) both predator types added to capture their interacting effect on ecosystem function (decomposition, nutrient release, and plant growth). Notably, the study resolved the causal pathways and strengths of direct and indirect control using structural equation modelling. These findings reveal how context dependency arises due to different capacities of the predators alone and together to overcome prey defences and control their abundances, with attendant cascading effects that diminished as well as enhanced decomposition and nutrient release to support bromeliad plant production. The study reveals that predators have a decided, albeit qualitatively and quantitatively different, hand in shaping the degree of bottom-up control through feedback effect on the release of limiting nutrients. This ground-breaking study provides a way forward in understanding the mechanisms determining context dependency in the control over ecosystem functioning.

A trait‐based understanding of the vulnerability of a Paleotropical moth community to predation by a sympatric bat with flexible foraging strategies

Abstract Prey vulnerability across seasons can be predicted by measuring their morphological traits and availability. Although conventional prey–predator dynamics focus on pairs of prey and predator species, the trait‐based approach allows us to draw inferences at the scale of the entire assemblage. Here, we coupled measurable prey traits with their availability in the study area, to identify the vulnerability of a diverse moth assemblage to predation by the lesser false vampire bat (Megaderma spasma) Chiroptera: Megadermatidae, Linneaus 1758, a bat with flexible foraging strategies, in the Western Ghats biodiversity hotspot of India. We analysed the discarded prey remains from several roosts, collected over 3 years, for seasonal patterns in the diet and selective hunting. Through light‐trapping, we collected moth specimens in different seasons and measured the morphological traits likely to affect their vulnerability to predation, such as body size and evasive flight capability. Our results showed that consumed moth prey diversity varies seasonally, with moths belonging to the Hepialidae family being preferred in the wet season. We found that the larger moth species with lower evasive capabilities are more vulnerable to predation. Sphingid and Hepialid moths, among the most abundant in the diet, have the lowest manoeuvrability and the maximum body size, respectively. By assessing vulnerability at the prey assemblage level, our study sets the stage for future research on moth–bat interactions from the diverse and less‐explored Paleotropical communities. In addition, the study reiterates the usefulness of trait‐based approaches to understanding prey–predator dynamics.

Trophic cascades within and across ecosystems: The role of anti-predatory defences, predator type and detritus quality.

Species in one ecosystem can indirectly affect multiple biodiversity components and ecosystem functions of adjacent ecosystems. The magnitude of these cross-ecosystem effects depends on the attributes of the organisms involved in the interactions, including traits of the predator, prey and basal resource. However, it is unclear how predators with cross-ecosystem habitat interact with predators with single-ecosystem habitat to affect their shared ecosystem. Also, unknown is how such complex top-down effects may be mediated by the anti-predatory traits of prey and quality of the basal resource. We used the aquatic invertebrate food webs in tank bromeliads as a model system to investigate these questions. We manipulated the presence of a strictly aquatic predator (damselfly larvae) and a predator with both terrestrial and aquatic habitats (spider), and examined effects on survival of prey (detritivores grouped by anti-predator defence), detrital decomposition (of two plant species differing in litter quality), nitrogen flux and host plant growth. To evaluate the direct and indirect effects each predator type on multiple detritivore groups and ultimately on multiple ecosystem processes, we used piecewise structural equation models. For each response variable, we isolated the contribution of different detritivore groups to overall effects by comparing alternate model formulations. Alone, damselfly larvae and spiders each directly decreased survival of detritivores and caused multiple indirect negative effects on detritus decomposition, nutrient cycling and host plant growth. However, when predators co-occurred, the spider caused a negative non-consumptive effect on the damselfly larva, diminishing the net direct and indirect top-down effects on the aquatic detritivore community and ecosystem functioning. Both detritivore traits and detritus quality modulated the strength and mechanism of these trophic cascades. Predator interference was mediated by undefended or partially defended detritivores as detritivores with anti-predatory defences evaded consumption by damselfly larvae but not spiders. Predators and detritivores affected ecosystem decomposition and nutrient cycling only in the presence of high-quality detritus, as the low-quality detritus was consumed more by microbes than invertebrates. The complex responses of this system to predators from both recipient and adjacent ecosystems highlight the critical role of maintaining biodiversity components across multiple ecosystems.

Factors related to sound production by the Chinese grasshopper Acrida cinerea during escape

Many grasshopper species produce conspicuous sounds while escaping from approaching predators; however, they occasionally escape without producing sounds. The Chinese grasshopper, Acrida cinerea, often exhibits noisy escape behavior. Therefore, a field experiment was conducted using A. cinerea to identify factors related to the production of sound during escape. This study utilized a predator model with an investigator approaching A. cinerea three times. We examined the relationship between the production of sound during escape and the following factors: ambient temperature and relative humidity as environmental factors; sex, body length, body weight, and limb autotomy as prey traits; and the repeated approach as a predator trait. The relationships between noisy escape and flight initiation distance (i.e., predator-prey distance when the prey initiates the escape), distance fled (i.e., distance the prey covered during the escape), and the mode of locomotion during escape (i.e., flying or jumping) were also examined. Noisy escape was observed only in males that escaped by flying, whereas the females and males that escaped by jumping invariably escaped silently. Among males that flew, noisy escape was related to ambient temperature, limb autotomy, and distance fled. The proportion that produced sound increased in parallel with the ambient temperature and distance fled. This proportion was lower among individuals that had autotomized one of their hind legs. These results indicate that noisy escape behavior is most frequent in healthy male A. cinerea under warm conditions.

Trait-based indicators of resource selection by albacore tuna in the California Current Large Marine Ecosystem

As global climate change reorganizes marine ecosystems, understanding how predators will respond to variable prey resources is critical to forecasting future community dynamics. Prey traits that affect the foraging process and recur across unrelated taxa offer a means to better anticipate predator resource use by simplifying complex foraging dynamics. Here we compare taxonomic and trait-based indicators of resource use and selection for albacore tuna (Thunnus alalunga), a commercially valuable pelagic predator undergoing climate-driven range shifts. We synthesized datasets from 2005 to 2019 to evaluate diets of albacore tuna in relation to prey availability estimates from shipboard surveys in the California Current Large Marine Ecosystem. Analyses with these data reveal that albacore and trawl surveys sample different aspects of the pelagic system, with albacore consuming a subset of taxa identified within trawls. Albacore consistently selected coastal prey that are schooling, undefended, silvered and countershaded, and have high energy density — suggesting that ecological mechanisms driving albacore foraging outcomes may be conserved across time and space. Ecological traits mediating predator-prey interactions consistently distinguished albacore diets from assemblages sampled by trawls across years and regions. We demonstrate that a traits-based approach simplifies taxonomically diverse predator-prey interactions and may be a valuable tool to facilitate predictions of prey resource use in changing environments.

Prey selection along a predators' body size gradient evidences the role of different trait-based mechanisms in food web organization.

An increase in prey richness, prey size and predator trophic position with predator body size has been consistently reported as prime features of food web organization. These trends have been explained by non-exclusive mechanisms. First, the increase in energy demand with body size determines that larger predators must reduce prey selectivity for achieving the required number of resources, being consumption relationships independent of prey traits. Second, when consumption is restricted by gape limitation, small predators are constrained to select among small prey. However, this selection weakens over large predators, which progressively consume more and larger prey. Finally, the optimal foraging mechanism predicts that larger predators optimize their diet by selecting only large prey with high energy reward. Each one of these mechanisms can individually explain the increase in prey richness, prey size and predator trophic position with predator body size but their relative importance or the direct evidence for their combined role was seldom considered. Here we use the community assembly by trait selection (CATS) theory for evaluating the support for each one of these mechanisms based on the prey selection patterns that they predict. We analyzed how prey body size and trophic guild determine prey selection by predators of increasing body size in a killifish guild from a temporary pond system. Results support the combination of the three mechanisms to explain the structural trends in our food web, although their strength is contingent on prey trophic group. Overall, high energy prey are preferred by larger predators, and small predators select small prey of all trophic status. However, large predators prefer large primary producers and avoid large carnivorous prey, probably because of the inherent risk of consuming other carnivorous. Our study provides a mechanistic understanding of how predator traits determine the selection of prey traits affecting food web assembly.

Functional identity of dominant species in a predator community prevails over functional diversity in shaping the top‐down control of herbivores

Abstract Decline in species richness as well as changes in community evenness or functional diversity have been hypothesised to jointly affect ecosystem functioning. However, disentangling the relative effects of these changes in community structure is hard as these different aspects often covary with species richness in real‐world ecosystems. In this study, we investigated the individual and interactive effects of functional diversity and community evenness of predators on the level of control of herbivorous prey. Using a highly replicated mesocosm experiment, we crossed three levels of functional diversity of arthropod predators with two levels of community evenness while controlling for the effect of species richness. Using this experimental setting, we hypothesised that the effect size of functional diversity of predators depends on community evenness. We expected a positive effect of functional diversity of predators on top‐down control at high level of community evenness while we thought that species identity and their associated traits should drive most of the effect on top‐down control at low level of community evenness. Our results did not provide any evidence for an interaction between functional diversity and community evenness nor any beneficial effect of increased functional diversity overall on predation rates of herbivorous prey. In addition, our results revealed that species and functional identity drives most of the effects of predator community composition on top‐down control of their prey in our study system. Assemblages composed of active hunters with low handling time and no starvation ability tended to have the highest impacts on prey biomass. By indicating that top‐down control of herbivorous prey by arthropod predators is mainly driven by species and functional identity and not by functional diversity, our study provides insights into the consequences of ongoing species loss on ecosystem functioning. Future research should now explore the predictability of trophic interactions based on functional traits of predator and herbivorous prey to anticipate the consequences of changes in species composition on ecosystem functioning. Read the free Plain Language Summary for this article on the Journal blog.

Changes in prey body size differentially reduces predation risk across predator and prey abundances

Trophic interactions underpin the structure of ecological communities by describing the rates at which consumers exploit their resources. The rates at which predators consume their prey are influenced by prey traits, with many species inducing defensive modifications to prey traits following the threat of predation. Here we use different clonal lines of the protist Paramecium being consumed by Stenostomum predators to highlight how differences in prey traits impact rates of predation. Clonal lines differed in their body width traits, and in their ability to induce changes in body width. By using a factorial cross of predator and prey abundances for different clonal lines we demonstrate how evolutionary or induced alterations in prey traits can impact the relative threat of predation. Our experiments show how interference among predators impacts predation rate, and how increased body width increased predator handling times. Given that reductions in the strength of interspecific interactions are associated with increased levels of overall community stability, our results indicate how individual level changes may scale up to impact whole communities.

Niche concept scale in space and time: evolutionary perspectives from tropical insectivorous birds

Ecological niches are pivotal in addressing questions of species richness gradients like the Latitudinal Diversity Gradient (LDG). The Hutchinsonian niche hypervolume model and derivatives are some of the most proven tools. Accordingly, species occupy mathematically convenient spaces in relation to functional, especially trophic, relationships, as well as the physical environment. In one application, the number of species in a community is a function of average niche sizes, overlaps, and total niche volume. Alternatively, the number of coexisting species derives from invasibility criteria in relation to species-interaction modules. The daunting complexity of tropical communities begs the question of how well these ecologically inspired paradigms accommodate present knowledge of species interactions and functional relationships. Recent studies of hyperdiverse tropical insectivorous bird species suggests reevaluating the applicability of such concepts. Here I review Neotropical, arthropod-feeding bird species interactions needed to explain these species’ trophic relationships, including their diets, feeding substrates, and behavioral and morphological traits relevant to resource acquisition. Important emergent generalizations include extraordinary specializations on both prey resource locations (substrates) and behaviors, rather than on particular resources per se, and a preponderance of adaptations to exploit the anti-predator traits of prey, traits evolved in response to other predators. These specializations and implicit arms races necessitate evolutionary approaches to niches necessary to understand the relevant natural history and ecology, how these species compete interspecifically, and even how these predator species interact with prey via evolutionary enhancements. These findings, compared and contrasted with prevailing concepts and findings, suggest expanding niche concepts to accommodate both the large temporal and regional geographic scales to understand the accumulated species richness of the mainland Neotropics. These trophic specializations also highlight why many of these birds are so sensitive to human disturbances, especially habitat loss, fragmentation, and degradation.

Fear of predators alters herbivore regulation of soil microbial community function.

Fear of predation can affect important ecosystem processes by altering the prey traits expression that, in turn, regulates the quantity and quality of nutritional inputs to soil. Here, we aimed to assist in bridging a knowledge gap in this cascading chain of events by exploring how risk of spider predation may affect grasshopper prey performances, and the activity of various microbial extracellular enzymes in the soil. Using a mesocosms field-experiment, we found that grasshoppers threatened by spider predation ate less, grew slower, and had a higher body carbon to nitrogen ratio. Herbivory increased activity of all microbial extracellular enzymes examined, likely due to higher availability of root exudates. Predation risk had no effect on C-acquiring enzymes but decreased activity of P-acquiring enzymes. We found contrasting results regarding the effect of predation on the activity of N-acetyl-glucosaminidase and leucine arylamidase N-acquiring enzymes, suggesting that predation risk may alter the composition of N-inputs to soil. Our work highlighted the importance of soil microbial enzymatic activity as a way to predict how changes in the aboveground food-web dynamics may alter key ecosystem processes like nutritional-cycling.

Body setae of a carnivorous caterpillar are an antagonistic trait against a defensive trait of prey: A case study of the aphidophagous larvae of Taraka hamada (Lepidoptera: Lycaenidae)

Abstract To feed on prey efficiently, predators must overcome the prey's defensive traits. However, there are fewer reports on the antagonistic traits of predators than there are on the defensive traits of prey. Here, we focus on prey–predator interactions between social aphids and aphidophagous lepidopteran larvae. Larvae of Taraka hamada (Lepidoptera: Lycaenidae) are specialist predators of the social aphid Ceratovacuna japonica (Homoptera: Aphididae), and later instar larvae have long lateral body setae. Because this aphid produces defensive individuals (soldiers), we hypothesised that T. hamada larvae have an antagonistic trait that prevents attacks by soldiers and tested whether that trait might be their lateral body setae. To test whether a larva's lateral body setae constitute an antagonistic trait against the soldier's physical defence, we compared the rate of aphid consumption per unit time and the vulnerability to attack by soldiers between larvae with short lateral body setae and larvae with long lateral body setae in the presence of soldiers. Our results showed that the aphid consumption rate of larvae with long lateral body setae was significantly higher than that of larvae with short lateral body setae. Furthermore, the larvae with short lateral body setae were more vulnerable to soldier attacks than the larvae with long lateral body setae. These results imply that the length of the lateral body setae of T. hamada larvae affects their vulnerability to soldier attacks and that the lateral body setae are an antagonistic trait against the soldiers of this social aphid.

Evolutionarily stable levels of aposematic defence in prey populations

Our understanding of aposematism (the conspicuous signalling of a defence for the deterrence of predators) has advanced notably since its first observation in the late nineteenth century. Indeed, it extends the scope of a well-established game-theoretical model of this very same process both from the analytical standpoint (by considering regimes of varying background mortality and colony size) and from the practical standpoint (by assessing its efficacy and limitations in predicting the evolution of prey traits in finite simulated populations). The nature of the manuscript at hand is more mathematical and its aim is two-fold: first, to determine the relationship between evolutionarily stable levels of defence and signal strength under various regimes of background mortality and colony size. Second, to compare these predictions with simulations of finite prey populations that are subject to random local mutation. We compare the roles of absolute resident fitness, mutant fitness and stochasticity in the evolution of prey traits and discuss the importance of population size in the above.

Partial refuges from biological control due to intraspecific variation in protective host traits.

Predicting how much of a host or prey population may be attacked by their natural enemies is fundamental to several subfields of applied ecology, particularly biological control of pest organisms. Hosts or prey can occupy refuges that prevent them from being killed by natural enemies, but habitat or ecological refuges are challenging or impossible to predict in a laboratory setting-which is often where efficacy and specificity testing of candidate biological control agents is done. Here we explore how intraspecific variation in continuous traits of individuals or groups that confer some protection from natural enemy attack-even after the natural enemy has encountered the prey-could provide partial refuges. The size of these trait-based refuges (i.e., the proportion of prey that survive natural enemy encounters due to protective traits) should depend on the relationship between trait values and host/prey susceptibility to natural enemy attack and on how common different trait values are within a host/prey population. These can be readily estimated in laboratory testing of natural enemy impact on target or nontarget prey or hosts as long as sufficient host material is available. We provide a general framework for how intraspecific variation in protective host traits could be integrated into biological control research, specifically with reference to nontarget testing as part of classical biological control programs. As a case study, we exposed different host clutch sizes of target (pest) and nontarget (native species) stink bug (Hemiptera: Pentatomidae) species to a well-studied exotic biocontrol agent, the egg parasitoid Trissolcus japonicus (Hymenoptera: Scelionidae). We predicted that the smallest and largest clutches would occupy trait-based refuges from parasitism. Although we observed several behavioral and reproductive responses to variation in host egg mass size by T. japonicus, they did not translate to increases in host survival large enough to change the conclusions of nontarget testing. We encourage researchers to investigate intraspecific variation in a wider variety of protective host and prey traits and their consequences for refuge size.

Predator-prey traits and foraging habitat shape the diet of a common insectivorous bat

Individual and species traits may determine the functional relationships between predators and their prey, with clear consequences for the ecosystem services potentially associated with predation. Bats are well-known potential deliverers of ecosystem services in agroecosystems through predation of pest arthropods that may affect crop production. Here we test the role of individual and prey traits in shaping the dietary habits of the Savi's pipistrelle (Hypsugo savii), a common bat species that frequently occurs in agroecosystems across the Mediterranean area, assessing diet composition and trait-based biases through molecular tools and multivariate testing techniques. DNA metabarcoding identified 173 distinct prey taxa in bats sampled in the Vesuvius National Park (Southern Italy). The diet was strongly dominated by pest insects associated with agricultural areas, which covered 57% of the overall prey diversity, some representing major pests of high economic relevance. The multivariate analyses detected strong relationships between diet composition, sampling date, and individual bat body conditions. Larger bats consumed larger prey items, and prey consumed later in the season (August) were smaller than those eaten in early summer (July) and were typical of less natural habitats. Hypsugo savii is potentially an important pest suppressor in the agroecosystems of the Mediterranean region and the functional relationships between the traits of individual bats and their prey set the basis for a quantitative assessment of the associated ecosystem service. We also remark on the value of bat diet studies in aiding the surveillance of arthropod species relevant to agriculture, human health, and biodiversity conservation.