Prey Phenotypes Research Articles

Urban socioeconomic variation influences the ecology and evolution of trophic interactions.

As urbanization expands, it is becoming increasingly important to understand how anthropogenic activity is affecting ecological and evolutionary processes. Few studies have examined how human social patterns within cities can modify eco-evolutionary dynamics. We tested how socioeconomic variation corresponds with changes in trophic interactions and natural selection on prey phenotypes using the classic interaction between goldenrod gall flies (Eurosta solidaginis) and their natural enemies: birds, beetles, and parasitoid wasps. We sampled galls from 84 sites across neighbourhoods with varying socioeconomic levels, and quantified the frequency of predation/parasitism on flies and natural selection by each enemy. We found that bird predation was higher in the highest income neighbourhoods, increasing the strength of selection for smaller galls. Wasp and beetle attack, but not their strength of selection, increased in lower income neighbourhoods. We show that socioeconomic variation in cities can have strong unintended consequences for the ecology and evolution of trophic interactions.

ANTI-APOSTATIC FEEDING BEHAVIOR IN TWO SPECIES OF ASSASSIN BUG, THE WHITE-SPOTTED ASSASSIN BUG PLATYMERIS BIGUTTATUS AND RED-SPOTTED ASSASSIN BUG PLATYMERIS RHADAMANTHUS (HEMIPTERA: REDUVIIDAE)

Abstract Predator-prey relationships are a driving force when examining community ecology. One question in predator-prey interactions is how a predator may respond to novel prey phenotypes, a form of frequency dependent prey selection. A predator may selectively target or avoid the novel prey, a behavior referred to as anti-apostatic or apostatic selection respectively. We examined apostatic prey selection by observing feeding behavior in two species of assassin bugs (Hemiptera: Reduviidae), the white-spotted assassin bug (Platymeris biguttatus) and the red-spotted assassin bug (Platymeris rhadamanthus) which were fed unmodified and modified (novel) phenotypes of Turkistan cockroaches, Blatta lateralis (Blattodea: Blattidae). The two species of assassin bugs represent either generalist (P. biguttatus) or specific feeders (P. rhadamanthus). We hypothesized that the generalist feeder would engage in anti-apostatic feeding while the specific feeder would engage in apostatic feeding. Our results indicated that there was no difference in feeding behavior between the two species, however an overall trend of apostatic feeding was observed in response to two of the four novel prey phenotypes. Factors beyond prey phenotype may also be influencing feeding choice in these insects. While the two predator species did not exhibit different feeding behaviors, the observation of apostatic feeding in this genus suggest an overall trend of utilizing specific prey images in feeding.

Development under predation risk increases serotonin-signaling, variability of turning behavior and survival in adult fruit flies Drosophila melanogaster.

The development of high-throughput behavioral assays, where numerous individual animals can be analyzed in various experimental conditions, has facilitated the study of animal personality. Previous research showed that isogenic Drosophila melanogaster flies exhibit striking individual non-heritable locomotor handedness. The variability of this trait, i.e., the predictability of left-right turn biases, varies across genotypes and under the influence of neural activity in specific circuits. This suggests that the brain can dynamically regulate the extent of animal personality. It has been recently shown that predators can induce changes in prey phenotypes via lethal or non-lethal effects affecting the serotonergic signaling system. In this study, we tested whether fruit flies grown with predators exhibit higher variability/lower predictability in their turning behavior and higher survival than those grown with no predators in their environment. We confirmed these predictions and found that both effects were blocked when flies were fed an inhibitor (αMW) of serotonin synthesis. The results of this study demonstrate a negative association between the unpredictability of turning behavior of fruit flies and the hunting success of their predators. We also show that the neurotransmitter serotonin controls predator-induced changes in the turning variability of fruit flies, regulating the dynamic control of behavioral predictability.

High predation risk decimates survival during the reproduction season.

Predators attack conspicuous prey phenotypes that are present in the environment. Male display behavior of conspicuous nuptial coloration becomes risky in the presence of a predator, and adult males face higher predation risk. High predation risk in one sex will lead to low survival and sex ratio bias in adult cohorts, unless the increased predation risk is compensated by higher escape rate.Here, we tested the hypothesis that sand lizards (Lacerta agilis) have sex‐specific predation risk and escape rate. We expected the differences to manifest in changes in sex ratio with age, differences in frequency of tail autotomy, and in sex‐specific survival rate.We developed a statistical model to estimate predation risk and escape rate, combining the observed sex ratio and frequency of tail autotomy with likelihood‐based survival rate. Using Bayesian framework, we estimated the model parameters. We projected the date of the tail autotomy events from growth rates derived from capture–recapture data measurements.We found statistically stable sex ratio in age groups, equal frequency of tail regenerates between sexes, and similar survival rate. Predation risk is similar between sexes, and escape rate increases survival by about 5%. We found low survival rate and a low number of tail autotomy events in females during months when sand lizards mate and lay eggs, indicating high predator pressure throughout reproduction. Our data show that gravid females fail to escape predation.The risks of reproduction season in an ectotherm are a convolution of morphological changes (conspicuous coloration in males and body allometry changes in gravid females), behavior (nuptial displays), and environmental conditions which challenge lizard thermal performance. Performance of endotherm predators in cold spring months endangers gravid females more than displaying males in bright nuptial coloration.

Evolution of population dynamics following invasion by a non-native predator.

Invasive predatory species are frequently observed to cause evolutionary responses in prey phenotypes, which in turn may lead to evolutionary shifts in the population dynamics of prey. Research has provided a link between rates of predation and the evolution of prey population growth in the lab, but studies from natural populations are rare. Here, we tested for evolutionary changes in population dynamics parameters of zooplankton Daphnia pulicaria following invasion by the predator Bythotrephes longimanus into Lake Kegonsa, Wisconsin, US. We used a resurrection ecological approach, whereby clones from pre‐ and post‐invasive periods were hatched from eggs obtained in sediment cores and were used in a 3‐month growth experiment. Based on these data, we estimated intrinsic population growth rates (r), the shape of density dependence (θ) and carrying capacities (K) using theta‐logistic models. We found that post‐invasion Daphnia maintained a higher r and K under these controlled, predation‐free laboratory conditions. Evidence for changes in θ was weaker. Whereas previous experimental evolution studies of predator–prey interactions have demonstrated that genotypes that have evolved under predation have inferior competitive ability when the predator is absent, this was not the case for the Daphnia. Given that our study was conducted in a laboratory environment and the possibility for genotype‐by‐environment interactions, extrapolating these apparent counterintuitive results to the wild should be done with caution. However, barring such complications, we discuss how selection for reduced predator exposure, either temporally or spatially, may have led to the observed changes. This scenario suggests that complexities in ecological interactions represents a challenge when predicting the evolutionary responses of population dynamics to changes in predation pressure in natural systems.

Prey defence phenotype mediates multiple-predator effects in tri-trophic food webs.

The emphasis on mechanisms governing the interaction among predators (e.g. cooperation, competition or intraguild predation) has driven the understanding of multiple-predator effects on prey survival and dynamics. However, overwhelming evidence shows that prey can adaptively respond to predators, exhibiting multiple defensive phenotypes to cope with predation. Nevertheless, there is still a relatively scarce theory connecting the emergence of prey defences in complex multi-predator scenarios and their ecological consequences. Using a mathematical approach, we evaluated the prevalence of defended prey phenotypes as a function of predator-induced mortality in a two-predator system, and how prey and phenotype dynamics affect trophic cascades. We also evaluated such responses when prey manifests a general defence against both predators (i.e. risk reducing) or a specialized defence against one predator at the expense of defence against the other predator (i.e. risk trade-off), and when such phenotypes induce fitness and foraging costs. We showed that the emergence of defended phenotypes under multiple predators depends on predator-induced mortality rates, the magnitude of phenotype costs and the effect of the defensive phenotype on the performance of all predators. Risk-reducing phenotypes enhance prioritized responses to predators with high killing rates, but prioritized responses are diminished when prey manifest risk trade-off phenotypes. Finally, we showed that resource abundance across the predation gradient directly depends on the prevalence of certain prey phenotypes and their effect on foraging costs. Ultimately, our results depict the implications of prey defences on prey and basal resources abundance in a multiple predators' environment, highlighting the role of the identity of defensive strategies in mediating the strength and nature of trophic cascades, via consumptive or non-consumptive effects.

Risk in one is not risk in all: snails show differential decision making under high- and low-risk environments

Predation is a major force that shapes prey phenotypes, species interactions and ecological communities. Prey respond to variation in predation risk and intensity by either increasing or decreasing vigilance and balancing energy requirements under high- or low-risk scenarios. We test the possible mechanism of sensory adaptation and decision making while responding to risk in the pond snail Lymnaea stagnalis . We maintained three risk treatment groups (no risk, low risk and high risk) for 20 days before testing them under multiple cognitive and behavioural challenges involving a predatory stimulus. Under a configural learning procedure where snails learned to forgo feeding when encountering food in the presence of a predatory threat, the high-risk group snails did not show learning/memory formation. However, when high-risk group individuals were transferred to a no-risk environment for 20 days, they were able to form configural learning memory. In a social interaction trial, snails from the no-risk group reduced interactions under threat whereas the high-risk group showed no change between risk environments. All risk groups responded similarly to an operant conditioning training under predation threat that enhanced memory. The decreased antipredator response of the high-risk group in comparison to the low-risk groups shows that snails are able to respond to risk based on past experience, especially when there exists a trade-off between survival and antipredator response. The variation in response to predation threat under different circumstances provides evidence of decision making rather than sensory adaptation as the mechanism involved in prey response. Our study combines multiple phenotypic responses to elucidate animal decision making under different intensities of risk and highlights the importance of experience in shaping antipredator responses. • We tested snails' responses (sensory adaptation/decision making) to predation risk. • Two cognitive tests and one social behavioural assay were used as response. • High-risk group animals showed weaker antipredator responses. • Response variation across risk groups support a decision-making mechanism at work.

Context-dependent coloration of prey and predator decision making in contrasting light environments.

A big question in behavioral ecology is what drives diversity of color signals. One possible explanation is that environmental conditions, such as light environment, may alter visual signaling of prey, which could affect predator decision-making. Here, we tested the context-dependent predator selection on prey coloration. In the first experiment, we tested detectability of artificial visual stimuli to blue tits (Cyanistes caeruleus) by manipulating stimulus luminance and chromatic context of the background. We expected the presence of the chromatic context to facilitate faster target detection. As expected, blue tits found targets on chromatic yellow background faster than on achromatic grey background whereas in the latter, targets were found with smaller contrast differences to the background. In the second experiment, we tested the effect of two light environments on the survival of aposematic, color polymorphic wood tiger moth (Arctia plantaginis). As luminance contrast should be more detectable than chromatic contrast in low light intensities, we expected birds, if they find the moths aversive, to avoid the white morph which is more conspicuous than the yellow morph in low light (and vice versa in bright light). Alternatively, birds may attack first moths that are more detectable. We found birds to attack yellow moths first in low light conditions, whereas white moths were attacked first more frequently in bright light conditions. Our results show that light environments affect predator foraging decisions, which may facilitate context-dependent selection on visual signals and diversity of prey phenotypes in the wild.

Prey preference of a wasp determined by nest size supports the role of natural selection in body size evolution in Cassidinae leaf beetles

Abstract The prey preference of a predator can impose natural selection on prey phenotypes, including body size. Despite evidence that large body size protects against predation in insects, the determinants of body size variation in Cassidinae leaf beetles are not well understood. We examined the prey preference of the digger wasp Cerceris albofasciata, a specialist predator of adult Cassidinae leaf beetles, and found evidence for natural selection on prey body size. The wasp hunted prey smaller than the size of their nest entrance. However, the wasp preferred larger prey species among those that could be carried into their nest. Thus, the benefits of large prey and the cost associated with nest expansion might determine the prey size preference. As expected from the prey species preference, the wasp preferred small individuals of the largest prey species, Thlaspida biramosa, and large individuals of the smallest prey species, Cassida piperata, resulting in natural selection on body sizes. In intermediate-sized prey species, however, there was no evidence for selection on body size. Natural selection on body size might explain the variation of prey morphologies that increase body size, such as explanate margins, in this group.

Predators override rainfall effects on tropical food webs

AbstractPredators alter ecological communities by inducing changes in prey abundance and phenotypes, including elemental and isotopic composition. Climatic factors are known to often moderate predator effects on prey abundance, but few studies consider the combined effects of climate and predators on prey phenotype. We examined how altered precipitation moderates the effects of predators on the abundance and the chemical composition of prey, as well as the indirect effects on the basal resource: leaf litter coated in biofilm. Using an experiment with an invertebrate food web module from tank bromeliads, we manipulated the presence of an odonate predator under scenarios of 10‐fold decreased, ambient, and threefold increased precipitation and measured responses of prey and their basal resource. Predators reduced prey abundance while precipitation did not. Both precipitation and predators, either singly or interactively, affected the elemental composition of prey. Predators increased C:N ratios of detritivorous beetles under high precipitation, but reduced the C:N ratio of the basal resource. Precipitation reduced the N content of filter‐feeding mosquitoes. The observed changes in chemical composition may reflect physiological or developmental responses to stress imposed by both predators and drought. This study demonstrates that the impact of predators and precipitation can vary substantially across a food web, including additive and synergistic effects, and numerical and phenotypic responses.Abstract in Spanish is available with online material.

Weak directional selection on inducible defensive shell traits in a marine gastropod by the inducing shell-breaking predator

Predation can drive variation in prey phenotypes by selecting for both constitutive and inducible defensive traits, which can act in concert to protect prey from predators. To understand the adaptive evolution of prey traits it is important to determine which traits are true targets of natural selection. Selection gradient analysis is a useful tool for doing this. We combined field surveys of the extensive intraspecific variation in defensive shell traits of the intertidal whelk Nucella lamellosa with laboratory experiments to determine which traits were associated with risk of crab predation, and which traits were under selection by the whelks’ major crab predator, Cancer productus. Field surveys showed strong associations between risk of crab predation and shell shape, shell thickness, and apertural area, but not apertural teeth. Laboratory choice experiments in which crabs were offered a variety of whelk shell morphs revealed that thinner–shelled whelks with wider apertures were consumed significantly more often than thicker–shelled whelks with narrower apertures, confirming previous findings, and resulting in positive selection differentials for these traits. However, multiple logistic regression revealed that only shell thickness, and none of the other traits measured, had a significant effect on whelk survival, indicating only weak directional selection for this trait. The mechanism for crabs selecting for shell thickness in whelks is likely through increased handling time and decreased profitability. Given that shell thickness is a phenotypically plastic trait induced by C. productus, future work should examine the degree to which selection by crabs acts on both constitutive levels and inducibility of shell thickness in N. lamellosa.

Coevolutionary patterns caused by prey selection

Many theoretical models have been formulated to better understand the coevolutionary patterns that emerge from antagonistic interactions. These models usually assume that the attacks by the exploiters are random, so the effect of victim selection by exploiters on coevolutionary patterns remains unexplored. Here we analytically studied the payoff for predators and prey under coevolution assuming that every individual predator can attack only a small number of prey any given time, considering two scenarios: (i) predation occurs at random; (ii) predators select prey according to phenotype matching. We also develop an individual based model to verify the robustness of our analytical prediction. We show that both scenarios result in well known similar coevolutionary patterns if population sizes are sufficiently high: symmetrical coevolutionary branching and symmetrical coevolutionary cycling (Red Queen dynamics). However, for small population sizes, prey selection can cause unexpected coevolutionary patterns. One is the breaking of symmetry of the coevolutionary pattern, where the phenotypes evolve towards one of two evolutionarily stable patterns. As population size increases, the phenotypes oscillate between these two values in a novel form of Red Queen dynamics, the episodic reversal between the two stable patterns. Thus, prey selection causes prey phenotypes to evolve towards more extreme values, which reduces the fitness of both predators and prey, increasing the likelihood of extinction.

Maternal predator-exposure affects offspring size at birth but not telomere length in a live-bearing fish.

The perception of predation risk could affect prey phenotype both within and between generations (via parental effects). The response to predation risk could involve modifications in physiology, morphology, and behavior and can ultimately affect long‐term fitness. Among the possible modifications mediated by the exposure to predation risk, telomere length could be a proxy for investigating the response to predation risk both within and between generations, as telomeres can be significantly affected by environmental stress. Maternal exposure to the perception of predation risk can affect a variety of offspring traits but the effect on offspring telomere length has never been experimentally tested. Using a live‐bearing fish, the guppy (Poecilia reticulata), we tested if the perceived risk of predation could affect the telomere length of adult females directly and that of their offspring with a balanced experimental setup that allowed us to control for both maternal and paternal contribution. We exposed female guppies to the perception of predation risk during gestation using a combination of both visual and chemical cues and we then measured female telomere length after the exposure period. Maternal effects mediated by the exposure to predation risk were measured on offspring telomere length and body size at birth. Contrary to our predictions, we did not find a significant effect of predation‐exposure neither on female nor on offspring telomere length, but females exposed to predation risk produced smaller offspring at birth. We discuss the possible explanations for our findings and advocate for further research on telomere dynamics in ectotherms.

Freshwater snail responses to fish predation integrate phenotypic plasticity and local adaptation

Predators shape the phenotype of prey by means of local adaptation, within-generation plasticity, and transgenerational plasticity. Theory predicts that the influence of these three mechanisms on phenotype is determined by the number of generations exposed to the predator and the autocorrelation between parent and offspring predator environments. To test theoretical predictions about the relative effects of local adaptation, within-generation plasticity, and transgenerational plasticity on prey phenotype, we exposed two generations of freshwater snails (Physa acuta) from two populations—one from a large pond containing predatory fish and one from a set of small ponds that lacked predatory fish—to the cues from a predaceous bluegill sunfish (Lepomis macrochirus). Physa acuta exhibit both local adaptation and phenotypic plasticity in response to predation risk; thus, we predicted that snails from the population with fish and snails experimentally exposed to fish cues would produce more globose (or spherical), crush-resistant shells. In addition, given the prolonged exposure to fish predation, we predicted that snails from the population with fish would exhibit reduced phenotypic plasticity. We found evidence that snails from the population with fish were generally more globose and more crush resistant than snails from the fish-less population and exposure to fish cues led snails from both populations to develop more globose shells with increased crush resistance. However, contrary to our predictions, the offspring of snails from both populations exposed to fish cues had elongated shells and reduced crush resistance. This may reflect the negative effects of parental stress or variation in resource investment.

Eco-evolutionary feedbacks link prey adaptation to predator performance.

Eco-evolutionary feedbacks may determine the outcome of predator-prey interactions in nature, but little work has been done to quantify the feedback effect of short-term prey adaptation on predator performance. We tested the effects of prey availability and recent (less than 100 years) prey adaptation on the feeding and growth rate of largemouth bass (Micropterus salmoides), foraging on western mosquitofish (Gambusia affinis). Field surveys showed higher densities and larger average body sizes of mosquitofish in recently introduced populations without bass. Over a six-week mesocosm experiment, bass were presented with either a high or low availability of mosquitofish prey from recently established populations either naive or experienced with bass. Naive mosquitofish were larger, less cryptic and more vulnerable to bass predation compared to their experienced counterparts. Bass consumed more naive prey, grew more quickly with naive prey, and grew more quickly per unit biomass of naive prey consumed. The effect of mosquitofish history with the bass on bass growth was similar in magnitude to the effect of mosquitofish availability. In showing that recently derived predation-related prey phenotypes strongly affect predator performance, this study supports the presence of reciprocal predator-prey trait feedbacks in nature.

Social information use about novel aposematic prey is not influenced by a predator's previous experience with toxins

Abstract Aposematism is an effective antipredator strategy. However, the initial evolution and maintenance of aposematism are paradoxical because conspicuous prey are vulnerable to attack by naïve predators. Consequently, the evolution of aposematic signal mimicry is also difficult to explain. The cost of conspicuousness can be reduced if predators learn about novel aposematic prey by observing another predator's response to that same prey. On the other hand, observing positive foraging events might also inform predators about the presence of undefended mimics, accelerating predation on both mimics and their defended models. It is currently unknown, however, how personal and social information combines to affect the fitness of aposematic prey. For example, does social information become more useful when predators have already ingested toxins and need to minimize further consumption? We investigated how toxin load influences great tits' (Parus major) likelihood to use social information about novel aposematic prey, and how it alters predation risk for undefended mimics. Birds were first provided with mealworms injected with bitter‐tasting chloroquine (or a water‐injected control), before information about a novel unpalatable prey phenotype was provided via video playback (either prey alone, or of a great tit tasting the noxious prey). An experimentally increased toxin load made great tits warier to attack prey, but only if they lacked social information about unpalatable prey. Socially educated birds consumed fewer aposematic prey relative to a cryptic phenotype, regardless of toxin load. In contrast, after personally experiencing aposematic prey, birds ignored social information about palatable mimics and were hesitant to sample them. Our results suggest that social information use by predators could be a powerful force in facilitating the evolution of aposematism as it reduces predation pressure on aposematic prey, regardless of a predator's toxin load. Nevertheless, observing foraging events of others is unlikely to alter frequency‐dependent dynamics among models and mimics, although this may depend on predators having recent personal experience of the model's unpalatability. A free Plain Language Summary can be found within the Supporting Information of this article.

Signal categorization by foraging animals depends on ecological diversity.

Warning signals displayed by defended prey are mimicked by both mutualistic (Müllerian) and parasitic (Batesian) species. Yet mimicry is often imperfect: why does selection not improve mimicry? Predators create selection on warning signals, so predator psychology is crucial to understanding mimicry. We conducted experiments where humans acted as predators in a virtual ecosystem to ask how prey diversity affects the way that predators categorize prey phenotypes as profitable or unprofitable. The phenotypic diversity of prey communities strongly affected predator categorization. Higher diversity increased the likelihood that predators would use a 'key' trait to form broad categories, even if it meant committing errors. Broad categorization favors the evolution of mimicry. Both species richness and evenness contributed significantly to this effect. This lets us view the behavioral and evolutionary processes leading to mimicry in light of classical community ecology. Broad categorization by receivers is also likely to affect other forms of signaling.

Evaluating the utility of camera traps in field studies of predation.

Artificial prey techniques—wherein synthetic replicas of real organisms are placed in natural habitats—are widely used to study predation in the field. We investigated the extent to which videography could provide additional information to such studies. As a part of studies on aposematism and mimicry of coral snakes (Micrurus) and their mimics, observational data from 109 artificial snake prey were collected from video-recording camera traps in three locations in the Americas (terra firme forest, Tiputini Biodiversity Station, Ecuador; premontane wet forest, Nahá Reserve, Mexico; longleaf pine forest, Southeastern Coastal Plain, North Carolina, USA). During 1,536 camera days, a total of 268 observations of 20 putative snake predator species were recorded in the vicinity of artificial prey. Predators were observed to detect artificial prey 52 times, but only 21 attacks were recorded. Mammals were the most commonly recorded group of predators near replicas (243) and were responsible for most detections (48) and attacks (20). There was no difference between avian or mammalian predators in their probability of detecting replicas nor in their probability of attacking replicas after detecting them. Bite and beak marks left on clay replicas registered a higher ratio of avian:mammalian attacks than videos registered. Approximately 61.5% of artificial prey monitored with cameras remained undetected by predators throughout the duration of the experiments. Observational data collected from videos could provide more robust inferences on the relative fitness of different prey phenotypes, predator behavior, and the relative contribution of different predator species to selection on prey. However, we estimate that the level of predator activity necessary for the benefit of additional information that videos provide to be worth their financial costs is achieved in fewer than 20% of published artificial prey studies. Although we suggest future predation studies employing artificial prey to consider using videography as a tool to inspire new, more focused inquiry, the investment in camera traps is unlikely to be worth the expense for most artificial prey studies until the cost:benefit ratio decreases.

Camouflage strategies interfere differently with observer search images.

Numerous animals rely on camouflage for defence. Substantial past work has identified the presence of multiple strategies for concealment, and tested the mechanisms underpinning how they work. These include background matching, D-RUP coloration to destroy target edges, and distractive markings that may divert attention from key target features. Despite considerable progress, work has focused on how camouflage types prevent initial detection by naive observers. However, predators will often encounter multiple targets over time, providing the opportunity to learn or focus attention through search images. At present, we know almost nothing about how camouflage types facilitate or hinder predator performance over repeated encounters. Here, we use experiments with human subjects searching for targets on touch screens with different camouflage strategies, and control the experience that subjects have with target types. We show that different camouflage strategies affect how subjects improve in detecting targets with repeated encounters, and how performance in detection of one camouflage type depends on experience of other strategies. In particular, disruptive coloration is effective at preventing improvements in camouflage breaking during search image formation, and experience with one camouflage type (distraction) can decrease the ability of subjects to switch to and from search images for new camouflage types (disruption). Our study is, to our knowledge, the first to show how the success of camouflage strategies depends on how they prevent initial and successive detection, and on predator experience of other strategies. This has implications for the evolution of prey phenotypes, how we assess the efficacy of defences, and predator–prey dynamics.

Inducible defense destabilizes predator–prey dynamics: the importance of multiple predators

Phenotypic plasticity in prey can have a dramatic impact on predator–prey dynamics, e.g. by inducible defense against temporally varying levels of predation. Previous work has overwhelmingly shown that this effect is stabilizing: inducible defenses dampen the amplitudes of population oscillations or eliminate them altogether. However, such studies have neglected scenarios where being protected against one predator increases vulnerability to another (incompatible defense). Here we develop a model for such a scenario, using two distinct prey phenotypes and two predator species. Each prey phenotype is defended against one of the predators, and vulnerable to the other. In strong contrast with previous studies on the dynamic effects of plasticity involving a single predator, we find that increasing the level of plasticity consistently destabilizes the system, as measured by the amplitude of oscillations and the coefficients of variation of both total prey and total predator biomasses. We explain this unexpected and seemingly counterintuitive result by showing that plasticity causes synchronization between the two prey phenotypes (and, through this, between the predators), thus increasing the temporal variability in biomass dynamics. These results challenge the common view that plasticity should always have a stabilizing effect on biomass dynamics: adding a single predator–prey interaction to an established model structure gives rise to a system where different mechanisms may be at play, leading to dramatically different outcomes.