Maternal effects and warning signal honesty in eggs and offspring of an aposematic ladybird beetle

Maternal Care Behavior and Its Consequences in Competition

Parental care behavior has evolved as a life history strategy to improve reproductive success, particularly in organisms facing challenging environments. However, the variation in maternal care, such as egg-guarding behavior in response to the social environment and the associated ecological consequence of competition, remains largely unknown. This study addresses a gap in current knowledge by examining the plasticity of maternal care behavior in the predatory mite C. eruditus and its impact on offspring survival and intra- and interspecific competition. Our results demonstrated that the reproductive females frequently exhibit egg-guarding behaviors, with enhanced maternal care efforts when the interspecific competitor is present. Egg masses are significantly more vulnerable to predation in the absence of maternal care. Guarding females increased egg survival rates and adversely influenced the survival of both con- and heterospecific competitors, with higher mortality rates being detected. Our findings highlight the ecological significance of maternal care behaviors and suggest that releasing C. eruditus and Neoseiulus cucumeris (Oudemans) together is not recommended for pest management in storage products.

The price of defence: toxins, visual signals and oxidative state in an aposematic butterfly

In a variety of aposematic species, the conspicuousness of an individual's warning signal and the quantity of its chemical defence are positively correlated. This apparent honest signalling is predicted by resource competition models which assume that the production and maintenance of aposematic defences compete for access to antioxidant molecules that have dual functions as pigments and in protecting against oxidative damage. To test for such trade-offs, we raised monarch butterflies (Danaus plexippus) on different species of their milkweed host plants (Apocynaceae) that vary in quantities of cardenolides to test whether (i) the sequestration of cardenolides as a secondary defence is associated with costs in the form of oxidative lipid damage and reduced antioxidant defences; and (ii) lower oxidative state is associated with a reduced capacity to produce aposematic displays. In male monarchs conspicuousness was explained by an interaction between oxidative damage and sequestration: males with high levels of oxidative damage became less conspicuous with increased sequestration of cardenolides, whereas those with low oxidative damage became more conspicuous with increased levels of cardenolides. There was no significant effect of oxidative damage or concentration of sequestered cardenolides on female conspicuousness. Our results demonstrate a physiological linkage between the production of coloration and oxidative state, and differential costs of sequestration and signalling in monarch butterflies.

A songbird can detect the eyes of conspecifics under daylight and artificial nighttime lighting

Eyes convey important information about the external and internal worlds of animals. Individuals can follow the gaze of others to learn about the location of salient objects as well as assess eye qualities to evaluate the health, age or other internal states of conspecifics. Because of the increasing prevalence of artificial lighting at night (ALAN), urbanized individuals can potentially garner information from conspecific eyes under both daylight and ALAN. We tested this possibility using a visual modeling approach in which we estimated the maximum distance at which individuals could detect conspecific eyes under daylight and high levels of ALAN. We also estimated the minimum light level at which individuals could detect conspecific eyes. Great-tailed grackles (Quiscalus mexicanus) were used as our study species because they are highly social and are unusual among birds in that they regularly gather at nocturnal roosts in areas with high levels of ALAN. This visual modelling approach revealed that grackles can detect conspecific eyes under both daylight and ALAN, regardless of iris coloration. The grackles could detect conspecific eyes at farther distances in daylight compared to ALAN. Our results highlight the potential importance of lighting conditions in shaping social interactions.

Egg toxic compounds in the animal kingdom. A comprehensive review

Covering: 1951 to 2022Packed with nutrients and unable to escape, eggs are the most vulnerable stage of an animal's life cycle. Consequently, many species have evolved chemical defenses and teamed up their eggs with a vast array of toxic molecules for defense against predators, parasites, or pathogens. However, studies on egg toxins are rather scarce and the available information is scattered. The aim of this review is to provide an overview of animal egg toxins and to analyze the trends and patterns with respect to the chemistry and biosynthesis of these toxins. We analyzed their ecology, distribution, sources, occurrence, structure, function, relative toxicity, and mechanistic aspects and include a brief section on the aposematic coloration of toxic eggs. We propose criteria for a multiparametric classification that accounts for the complexity of analyzing the full set of toxins of animal eggs. Around 100 properly identified egg toxins are found in 188 species, distributed in 5 phyla: cnidarians (2) platyhelminths (2), mollusks (9), arthropods (125), and chordates (50). Their scattered pattern among animals suggests that species have evolved this strategy independently on numerous occasions. Alkaloids are the most abundant and widespread, among the 13 types of egg toxins recognized. Egg toxins are derived directly from the environment or are endogenously synthesized, and most of them are transferred by females inside the eggs. Their toxicity ranges from ρmol kg^-1 to mmol kg^-1, and for some species, experiments support their role in predation deterrence. There is still a huge gap in information to complete the whole picture of this field and the number of toxic eggs seems largely underestimated.

How Diet Leads to Defensive Dynamism: Effect of the Dietary Quality on Autogenous Alkaloid Recovery Rate in a Chemically Defended Beetle

The impact of different diets on chemical defense has been extensively studied in animals that sequester defensive chemicals from food. However, there are fewer studies of diet-mediated variation in autogenously produced defenses. Ladybird beetles, which use autogenously synthesized defensive alkaloids, are used as models in a wide diversity of studies of chemical defense, specifically in studies of intraspecific variation in color pattern and chemical defense. Many aphidophagous ladybirds consume a wide diversity of aphid prey, which vary in quality and thus could affect the synthesis of chemical defense. We measured alkaloid recovery rate after reflex bleeding by the ladybird Adalia bipunctata on two different aphid diets, the high quality Acyrthosiphon pisum and the lower quality Aphis fabae. Alkaloids reaccumulated in ladybirds more slowly when they were fed A. fabae than when they were fed A. pisum and females generally had more alkaloid than males, but reaccumulated alkaloid more slowly. Recovery times were more than 12 days. There appeared to be a weak positive relationship between alkaloid level and time since reflex bleeding for eggs of A. pisum- but not A. fabae-fed females. Our findings on diet and alkaloid synthesis in ladybirds suggest that chemical defense levels are very dynamic, indicating that studies conducted at a single point in time, such as those focused on ladybird color pattern, fail to consider a wide diversity of temporal variation that occurs in the field. This is likely true for many autogenously produced chemical defense systems in a diversity of other organisms.

Evolutionary and ecological processes influencing chemical defense variation in an aposematic and mimetic Heliconius butterfly

Chemical defences against predators underlie the evolution of aposematic coloration and mimicry, which are classic examples of adaptive evolution. Surprisingly little is known about the roles of ecological and evolutionary processes maintaining defence variation, and how they may feedback to shape the evolutionary dynamics of species. Cyanogenic Heliconius butterflies exhibit diverse warning color patterns and mimicry, thus providing a useful framework for investigating these questions. We studied intraspecific variation in de novo biosynthesized cyanogenic toxicity and its potential ecological and evolutionary sources in wild populations of Heliconius erato along environmental gradients, in common-garden broods and with feeding treatments. Our results demonstrate substantial intraspecific variation, including detectable variation among broods reared in a common garden. The latter estimate suggests considerable evolutionary potential in this trait, although predicting the response to selection is likely complicated due to the observed skewed distribution of toxicity values and the signatures of maternal contributions to the inheritance of toxicity. Larval diet contributed little to toxicity variation. Furthermore, toxicity profiles were similar along steep rainfall and altitudinal gradients, providing little evidence for these factors explaining variation in biosynthesized toxicity in natural populations. In contrast, there were striking differences in the chemical profiles of H. erato from geographically distant populations, implying potential local adaptation in the acquisition mechanisms and levels of defensive compounds. The results highlight the extensive variation and potential for adaptive evolution in defense traits for aposematic and mimetic species, which may contribute to the high diversity often found in these systems.

Meta-analytic evidence for quantitative honesty in aposematic signals

The combined use of noxious chemical defences and conspicuous warning colours is a ubiquitous anti-predator strategy. That such signals advertise the presence of defences is inherent to their function, but their predicted potential for quantitative honesty-the positive scaling of signal salience with the strength of protection-is the subject of enduring debate. Here, we systematically synthesized the available evidence to test this prediction using meta-analysis. We found evidence for a positive correlation between warning colour expression and the extent of chemical defences across taxa. Notably, this relationship held at all scales; among individuals, populations and species, though substantial between-study heterogeneity remains unexplained. Consideration of the design of signals revealed that all visual features, from colour to contrast, were equally informative of the extent of prey defence. Our results affirm a central prediction of honesty-based models of signal function and narrow the scope of possible mechanisms shaping the evolution of aposematism. They suggest diverse pathways to the encoding and exchange of information, while highlighting the need for deeper knowledge of the ecology of chemical defences to enrich our understanding of this widespread anti-predator adaptation.

Drosophila melanogaster cloak their eggs with pheromones, which prevents cannibalism

Oviparous animals across many taxa have evolved diverse strategies that deter egg predation, providing valuable tests of how natural selection mitigates direct fitness loss. Communal egg laying in nonsocial species minimizes egg predation. However, in cannibalistic species, this very behavior facilitates egg predation by conspecifics (cannibalism). Similarly, toxins and aposematic signaling that deter egg predators are often inefficient against resistant conspecifics. Egg cannibalism can be adaptive, wherein cannibals may benefit through reduced competition and added nutrition, but since it reduces Darwinian fitness, the evolution of anticannibalistic strategies is rife. However, such strategies are likely to be nontoxic because deploying toxins against related individuals would reduce inclusive fitness. Here, we report how D. melanogaster use specific hydrocarbons to chemically mask their eggs from cannibal larvae. Using an integrative approach combining behavioral, sensory, and mass spectrometry methods, we demonstrate that maternally provisioned pheromone 7,11-heptacosadiene (7,11-HD) in the eggshell’s wax layer deters egg cannibalism. Furthermore, we show that 7,11-HD is nontoxic, can mask underlying substrates (for example, yeast) when coated upon them, and its detection requires pickpocket 23 (ppk23) gene function. Finally, using light and electron microscopy, we demonstrate how maternal pheromones leak-proof the egg, consequently concealing it from conspecific larvae. Our data suggest that semiochemicals possibly subserve in deceptive functions across taxa, especially when predators rely on chemical cues to forage, and stimulate further research on deceptive strategies mediated through nonvisual sensory modules. This study thus highlights how integrative approaches can illuminate our understanding on the adaptive significance of deceptive defenses and the mechanisms through which they operate.

Egg-laying species that lack parental care often protect their eggs from predators by laying them in communal groups or by fortifying them with toxins. However, these strategies may backfire when the predators are from the same species (cannibals) since a) there are plenty of available eggs in these sites, b) the cannibals may be resistant to the toxins, and c) poisoning cannibals who may be related would reduce inclusive fitness. Under these circumstances, natural selection should favor anticannibalistic strategies that are likely to be nontoxic. Here, we investigate how fruit flies (Drosophila melanogaster), which oviposit communally, protect their eggs from cannibalism by their own larvae. We show that maternal hydrocarbons incorporated into the egg’s wax layer to make them waterproof interestingly also serve as a mask that conceals their identity from cannibal larvae. In particular, we identify one female sex pheromone that deters cannibalism by forming a layer around the egg to conceal it. We further demonstrate that this pheromone is nontoxic and can mask underlying substrates such as yeast when used as a coating. While deceptive strategies (such as camouflage) deployed to avoid predation are extensively studied from a visual perspective, our findings suggest that deceptive strategies operating through other nonvisual sensory systems might be equally common across taxa.

Resolving tradeoffs among crypsis, escape behavior, and microhabitat use in sexually dichromatic species

Variation in color pattern between populations of cryptic animals is common and typically attributed to selection pressures from visual predators combined with variation in substrate composition. However, little is known about how cryptic color pattern relates to varied rates of predation, and few studies simultaneously analyze patterns of escape behavior and microhabitat use along with variation in color pattern, even though these traits evolve in tandem. Here, we use a combination of calibrated photographs and spectrometry to examine the influence of spatial heterogeneity in rates of predation on dorsal brightness in the Florida scrub lizard (Sceloporus woodi), a cryptic and sexually dimorphic species. Simultaneously, we analyze patterns of escape behavior and microhabitat use measured in the field. The results of this study indicate that populations inhabiting environments of increased predation have less color variation and more closely match the color of local substrate than populations sampled in environments of relaxed predation. Populations exposed to increased predation also show more pronounced escape behavior and are more selective in their use of microhabitat. Interestingly, geographic variation of dorsal brightness, escape behavior, and microhabitat use were greater for females than for males. Our results not only provide empirical evidence for theories of adaptive coloration, but suggest that sexual dichromatism can be maintained by selection pressures related to predation.

Morphological and biological characterization of a light-colored mutant in the multicolored Asian lady beetle, Harmonia axyridis

Insect cuticle color formed with melanin pigments has numerous types of mutants which usually cause pleiotropic effects. Melanism has been widely studied, but mutants with light-colored phenotype as well as the consequent fitness changes have rarely been reported.Here, in the laboratory strain of Harmonia axyridis, we found a novel mutant gr and confirmed that the mutation was inherited in a simple Mendelian autosomal recessive manner. This mutant (HAM) continuously displayed a light-colored pigmentation versus dark blackish in the wild phenotype (HAW). L-DOPA and dopamine are melanin precursors, and less L-DOPA was present in the cuticle of larval and adult HAM mutants compared to HAW wild type, but more dopamine was detected in the larval cuticle of HAM (p ≤ 0.0235). For the orange background of elytra, the composition as well as total concentration of carotenoids was different between HAM and HAW, which resulted in significantly lower saturation value but significantly higher hue value in HAM than in HAW (p < 0.0001).Extensive fitness changes were detected in HAM. (a) HAM larvae had similar predation capacity and preimaginal development time as HAW, but the newly emerged adults were much smaller (p < 0.0001). (b) Both fecundity and egg hatch rate in cross ♀(HAM) × ♂(HAM) were significantly lower than those in ♀(HAW) × ♂(HAW) (p ≤ 0.0087), but were not different with those in ♀(HAW) × ♂(HAM).

Diversity in warning coloration: selective paradox or the norm?

Aposematic theory has historically predicted that predators should select for warning signals to converge on a single form, as a result of frequency‐dependent learning. However, widespread variation in warning signals is observed across closely related species, populations and, most problematically for evolutionary biologists, among individuals in the same population. Recent research has yielded an increased awareness of this diversity, challenging the paradigm of signal monomorphy in aposematic animals. Here we provide a comprehensive synthesis of these disparate lines of investigation, identifying within them three broad classes of explanation for variation in aposematic warning signals: genetic mechanisms, differences among predators and predator behaviour, and alternative selection pressures upon the signal. The mechanisms producing warning coloration are also important. Detailed studies of the genetic basis of warning signals in some species, most notably Heliconius butterflies, are beginning to shed light on the genetic architecture facilitating or limiting key processes such as the evolution and maintenance of polymorphisms, hybridisation, and speciation. Work on predator behaviour is changing our perception of the predator community as a single homogenous selective agent, emphasising the dynamic nature of predator–prey interactions. Predator variability in a range of factors (e.g. perceptual abilities, tolerance to chemical defences, and individual motivation), suggests that the role of predators is more complicated than previously appreciated. With complex selection regimes at work, polytypisms and polymorphisms may even occur in Müllerian mimicry systems. Meanwhile, phenotypes are often multifunctional, and thus subject to additional biotic and abiotic selection pressures. Some of these selective pressures, primarily sexual selection and thermoregulation, have received considerable attention, while others, such as disease risk and parental effects, offer promising avenues to explore. As well as reviewing the existing evidence from both empirical studies and theoretical modelling, we highlight hypotheses that could benefit from further investigation in aposematic species. Finally by collating known instances of variation in warning signals, we provide a valuable resource for understanding the taxonomic spread of diversity in aposematic signalling and with which to direct future research. A greater appreciation of the extent of variation in aposematic species, and of the selective pressures and constraints which contribute to this once‐paradoxical phenomenon, yields a new perspective for the field of aposematic signalling.

Sex differences but no evidence of quantitative honesty in the warning signals of six-spot burnet moths (Zygaena filipendulae L.)

The distinctive black and red wing pattern of six-spot burnet moths (Zygaena filipendulae, L.) is a classic example of aposematism, advertising their potent cyanide-based defences. While such warning signals provide a qualitatively honest signal of unprofitability, the evidence for quantitative honesty, whereby variation in visual traits could provide accurate estimates of individual toxicity, is more equivocal. Combining measures of cyanogenic glucoside content and wing color from the perspective of avian predators, we investigate the relationship between coloration and defences in Z. filipendulae, to test signal honesty both within and across populations. There were no significant relationships between mean cyanogenic glucoside concentration and metrics of wing coloration across populations in males, yet in females higher cyanogenic glucoside levels were associated with smaller and lighter red forewing markings. Trends within populations were similarly inconsistent with quantitative honesty, and persistent differences between the sexes were apparent: larger females, carrying a greater total cyanogenic glucoside load, displayed larger but less conspicuous markings than smaller males, according to several color metrics. The overall high aversiveness of cyanogenic glucosides and fluctuations in color and toxin levels during an individual's lifetime may contribute to these results, highlighting generally important reasons why signal honesty should not always be expected in aposematic species.

Convergent evolution of plant and animal embryo defences by hyperstable non-digestible storage proteins

Plants have evolved sophisticated embryo defences by kinetically-stable non-digestible storage proteins that lower the nutritional value of seeds, a strategy that have not been reported in animals. To further understand antinutritive defences in animals, we analysed PmPV1, massively accumulated in the eggs of the gastropod Pomacea maculata, focusing on how its structure and structural stability features affected its capacity to withstand passage through predator guts. The native protein withstands >50 min boiling and resists the denaturing detergent sodium dodecyl sulphate (SDS), indicating an unusually high structural stability (i.e., kinetic stability). PmPV1 is highly resistant to in vitro proteinase digestion and displays structural stability between pH 2.0-12.0 and 25-85 °C. Furthermore, PmPV1 withstands in vitro and mice digestion and is recovered unchanged in faeces, supporting an antinutritive defensive function. Subunit sequence similarities suggest a common origin and tolerance to mutations. This is the first known animal genus that, like plant seeds, lowers the nutritional value of eggs by kinetically-stable non-digestible storage proteins that survive the gut of predators unaffected. The selective pressure of the harsh gastrointestinal environment would have favoured their appearance, extending by convergent evolution the presence of plant-like hyperstable antinutritive proteins to unattended reproductive stages in animals.

Diversity in warning coloration is easily recognized by avian predators

Warning coloration is a widespread strategy to alert predators about prey unprofitability. The success of this strategy partly depends on predators being able to learn and recognize certain signals as indicators of toxicity, and theory predicts that this is easier if signals converge on similar colours. However, the diversity in warning signal form is astonishing, contradicting predictions. Here, we quantified ladybird signal diversity with respect to avian vision, measuring how unique and discernible each signal is from one another. In addition, we measured signal conspicuousness against a series of backgrounds, namely an average green, average brown, and where we collected each species, to determine whether signals are more contrasting against the ladybirds' local substrates than compared to average ones. This allowed us to establish whether there are local adaptations in conspicuousness that promote signal diversity. We found that while ladybird signals are unique and recognizable, specialist species are more contrasting against the background they are most commonly found on. However, overall our study suggests that warning signals have evolved to be effective against a wide range of natural backgrounds, partly explaining the success of this strategy in nature.

Patterns and Drivers of Egg Pigment Intensity and Colour Diversity in the Ocean: A Meta-Analysis of Phylum Echinodermata

Egg pigmentation is proposed to serve numerous ecological, physiological, and adaptive functions in egg-laying animals. Despite the predominance and taxonomic diversity of egg layers, syntheses reviewing the putative functions and drivers of egg pigmentation have been relatively narrow in scope, centring almost exclusively on birds. Nonvertebrate and aquatic species are essentially overlooked, yet many of them produce maternally provisioned eggs in strikingly varied colours, from pale yellow to bright red or green. We explore the ways in which these colour patterns correlate with behavioural, morphological, geographic and phylogenetic variables in extant classes of Echinodermata, a phylum that has close phylogenetic ties with chordates and representatives in nearly all marine environments. Results of multivariate analyses show that intensely pigmented eggs are characteristic of pelagic or external development whereas pale eggs are commonly brooded internally. Of the five egg colours catalogued, orange and yellow are the most common. Yellow eggs are a primitive character, associated with all types of development (predominant in internal brooders), whereas green eggs are always pelagic, occur in the most derived orders of each class and are restricted to the Indo-Pacific Ocean. Orange eggs are geographically ubiquitous and may represent a 'universal' egg pigment that functions well under a diversity of environmental conditions. Finally, green occurs chiefly in the classes Holothuroidea and Ophiuroidea, orange in Asteroidea, yellow in Echinoidea, and brown in Holothuroidea. By examining an unprecedented combination of egg colours/intensities and reproductive strategies, this phylum-wide study sheds new light on the role and drivers of egg pigmentation, drawing parallels with theories developed from the study of more derived vertebrate taxa. The primary use of pigments (of any colour) to protect externally developing eggs from oxidative damage and predation is supported by the comparatively pale colour of equally large, internally brooded eggs. Secondarily, geographic location drives the evolution of egg colour diversity, presumably through the selection of better-adapted, more costly pigments in response to ecological pressure.

The eggs of the apple snail Pomacea maculata are defended by indigestible polysaccharides and toxic proteins

The freshwater snails Pomacea Perry, 1810 lay conspicuous aerial egg clutches that are ignored by most predators. Egg biochemical defenses in the apple snail Pomacea canaliculata (Lamarck, 1822) are provided by multifunctional proteins. We analyzed the eggs of a sympatric species, Pomacea maculata Perry, 1810, studying the gross composition, toxicity, hemagglutinating activity, and its antinutritive and antidigestive properties. Eggs are mostly composed of polysaccharides (mainly galactogen) and proteins, followed by lipids and nonsoluble calcium. Two perivitellins account for ∼85% dry mass of the egg protein. The major lipids are phospholipids and sterols. A suite of potential defenses was determined, including strong lethal neurotoxicity on mice and moderate antidigestive and lectin activities. Remarkably, their polysaccharides were refractive to in vitro digestion by digestive glycosidases. This study characterized ∼99% of egg composition and identified multiple potential defenses, provided not only by proteins but also by polysaccharides. This is the first evidence to our knowledge that reserve sugars may be involved in defenses, giving further insight into the unusual reproductive strategy of these well-defended snail eggs.

Reproduction in Risky Environments: The Role of Invasive Egg Predators in Ladybird Laying Strategies

Reproductive environments are variable and the resources available for reproduction are finite. If reliable cues about the environment exist, mothers can alter offspring phenotype in a way that increases both offspring and maternal fitness (‘anticipatory maternal effects’—AMEs). Strategic use of AMEs is likely to be important in chemically defended species, where the risk of offspring predation may be modulated by maternal investment in offspring toxin level, albeit at some cost to mothers. Whether mothers adjust offspring toxin levels in response to variation in predation risk is, however, unknown, but is likely to be important when assessing the response of chemically defended species to the recent and pervasive changes in the global predator landscape, driven by the spread of invasive species. Using the chemically defended two-spot ladybird, Adalia bipunctata, we investigated reproductive investment, including egg toxin level, under conditions that varied in the degree of simulated offspring predation risk from larval harlequin ladybirds, Harmonia axyridis. H. axyridis is a highly voracious alien invasive species in the UK and a significant intraguild predator of A. bipunctata. Females laid fewer, larger egg clusters, under conditions of simulated predation risk (P+) than when predator cues were absent (P-), but there was no difference in toxin level between the two treatments. Among P- females, when mean cluster size increased there were concomitant increases in both the mass and toxin concentration of eggs, however when P+ females increased cluster size there was no corresponding increase in egg toxin level. We conclude that, in the face of offspring predation risk, females either withheld toxins or were physiologically constrained, leading to a trade-off between cluster size and egg toxin level. Our results provide the first demonstration that the risk of offspring predation by a novel invasive predator can influence maternal investment in toxins within their offspring.

Signal honesty and predation risk among a closely related group of aposematic species

Many animals have bright colours to warn predators that they have defences and are not worth attacking. However, it remains unclear whether the strength of warning colours reliably indicate levels of defence. Few studies have unambiguously established if warning signals are honest, and have rarely considered predator vision or conspicuousness against the background. Importantly, little data exists either on how differences in signal strength translate into survival advantages. Ladybirds exhibit impressive variation in coloration both among and within species. Here we demonstrate that different levels of toxicity exist among and within ladybird species, and that signal contrast against the background is a good predictor of toxicity, showing that the colours are honest signals. Furthermore, field experiments with ladybird models created with regards to predator vision show that models with lower conspicuousness were attacked more frequently. This provides one of the most comprehensive studies on signal honesty in warning coloration to date.

Antagonistic evolution in an aposematic predator-prey signaling system

Warning signals within species, such as the bright colors of chemically defended animals, are usually considered mutualistic, monomorphic traits. Such a view is however increasingly at odds with the growing empirical literature, showing nontrivial levels of signal variation within prey populations. Key to understanding this variation, we argue, could be a recognition that toxicity levels frequently vary within populations because of environmental heterogeneity. Inequalities in defense may undermine mutualistic monomorphic signaling, causing evolutionary antagonism between loci that determine appearance of less well-defended and better defended prey forms within species. In this article, we apply a stochastic model of evolved phenotypic plasticity to the evolution of prey signals. We show that when toxicity levels vary, then antagonistic interactions can lead to evolutionary conflict between alleles at different signaling loci, causing signal evolution, "red queen-like" evolutionary chase, and one or more forms of signaling equilibria. A key prediction is that variation in the way that predators use information about toxicity levels in their attack behaviors profoundly affects the evolutionary characteristics of the prey signaling systems. Environmental variation is known to cause variation in many qualities that organisms signal; our approach may therefore have application to other signaling systems.