Presence Of Predator Cues Research Articles

Diversity of foraging strategies and responses to predator interference in seed-eating carabid beetles

The prediction of pest regulation by multi-predator communities often remains challenging because of variable and opposite effects of niche complementarity and predator interference. Carabid communities are regulating weeds in arable fields and include a mix of species ranging from granivores to predators that are obligate omnivores. It is not clear from field studies whether granivore and obligate omnivore species either contribute equally or are complementary in the process of weed suppression, and little is known about the impact of potential predator interference within carabid communities on weed suppression. We compared the weed seed foraging strategy of the granivore Harpalus affinis and the obligate omnivore Poecilus cupreus. Using no-choice test experiments, we compared their activity and seed acceptance for four weed species through a scoring of the proportion of tested individuals consuming weeds, their latency before the consumption of the first seed and the total number of seeds consumed. We then evaluated their seed acceptance for dandelion seed Taraxacum officinale under predator interference by using chemical cues of carabids and tested the impact of three treatments, namely cues of intraspecific competition, interspecific competition and intraguild predation. We found that the obligate omnivore P. cupreus was highly active, had a low latency before consuming its first seed but had an interest in only two of the four weed species. P. cupreus seed acceptance remained unchanged in the presence of predator cues. By contrast, H. affinis was slow to start its seed consumption, accepted equally seeds of the four weed species and significantly increased its seed consumption in the presence of cues mimicking intraguild predation. These findings indicate that the two species differ in their foraging strategies, and as such, could have different contributions to weed seed suppression. This novel result calls for further studies documenting the foraging strategy of carabid species that thrive in arable fields as this could significantly improve our understanding of the delivery of weed seed regulation.

A three‐dimensional perspective of Daphnia’s swimming behavior with and without predator cues

AbstractBehavioral adaptations play an important role in predator–prey interactions as they reduce predation risk. Prey organisms have therefore evolved a tremendous variability in behavioral adaptations. In case of small crustaceans of the genus Daphnia, which are common and important herbivores transferring energy from primary producers to higher trophic levels, such as predatory fish, and insects, altered migration patterns, swarming, or adaptive swimming speeds may increase survival rates. However, hitherto it has been difficult to analyze predator‐induced behavioral adaptations as the small body size, as well as the low contrast between the transparent animals and their environment, most often impede behavioral movement analysis of individual animals. Therefore, we worked with a newly established technique providing higher contrast. We tagged daphniids with fluorescent nanoparticles and used a three‐dimensional movement analysis system. We analyzed behavioral defense strategies of Daphnia clones from three species against different types of predators by measuring their behavior in presence and absence of predator cues. We analyzed swimming speed, depth selection, and motion patterns of Daphnia, as well as swarming behavior. We observed differences in the general swimming behavior in all analyzed aspects and show that daphniids change their behavioral strategies in the presence of predator cues, e.g., decrease their swimming speed as well as their vertical position or increase their nearest neighbor distance. Based on the observed changes in behavioral patterns, we conclude that the swimming behavior of daphniids may play an important role as inducible defense strategy that has the potential to improve prey survival chances.

Feeding behavior under predatory risk in Ctenomys talarum: nutritional state and recent experience of a predatory event

Predatory risk is recognized as an important factor that impacts on behavior, distribution, and reproduction of animals. Facing the presence of predators’ cues, preys have developed a series of anti-predatory behaviors that involve trade-offs between costs and benefits. Faced with the clear advantage of reducing the immediate risk of predation, preys are forced to modify their performance in other activities. The most documented of them is undoubtedly the foraging. In the presence of predators or their cues in the environment, a compromise between food and safety arises, so that the prey restricts the time searching for food, limits it to protected sites, or increase the vigilance, thus impacting foraging success and consequently in reproductive performance and long-term survival. However, the influence of several factors, like nutritional condition (fed or food deprived) or predator experience, on preys’ feeding choices has been comparatively less studied. Therefore, the aim of this work was to evaluate Ctenomys talarum’s feeding behavior under the presence of predator cues (cat urine) considering (1) their nutritional condition and (2) a recent experience of a failed predatory event. The results of this work show that tuco-tucos can distinguish cues indicative of the presence of a predator and prefer to feed in areas where predator cues are not present (safe sites). Also, recent predatory experiences influenced foraging decisions, increasing the time without activity previous to a new feeding excursion. In conclusion, these results demonstrate the importance of the perception of predatory risk in the foraging behavior of C. talarum.

Immune deployment increases larval vulnerability to predators and inhibits adult life‐history traits in a dragonfly

While deploying immune defences early in ontogeny can trade-off with the production and maintenance of other important traits across the entire life cycle, it remains largely unexplored how features of the environment shape the magnitude or presence of these lifetime costs. Greater predation risk during the juvenile stage may particularly influence such costs by (1) magnifying the survival costs that arise from any handicap of juvenile avoidance traits and/or (2) intensifying allocation trade-offs with important adult traits. Here, we tested for predator-dependent costs of immune deployment within and across life stages using the dragonfly, Pachydiplax longipennis. We first examined how larval immune deployment affected two traits associated with larval vulnerability to predators: escape distance and foraging under predation risk. Larvae that were induced to mount an immune response had shorter escape distances but lower foraging activity in the presence of predator cues. We also induced immune responses in larvae and reared them through emergence in mesocosms that differed in the presence of large predatory dragonfly larvae (Aeshnidae spp.). Immune-challenged larvae had later emergence overall and lower survival in pools with predators. Immune-challenged males were also smaller at emergence and developed less sexually selected melanin wing coloration, but these effects were independent of predator treatment. Overall, these results highlight how mounting an immune defence early in ontogeny can have substantial ecological and physiological costs that manifest both within and across life stages.

Elevated temperatures suppress inducible defenses and alter shell shape of intertidal mussel

As ocean temperatures continue to rise due to climate change, many questions remain on how coastal species will cope with a changing environment. The effects of increased temperatures on bivalves has been well examined through single-species studies, showing reductions in tissue mass, shell growth, oxygen uptake, feeding rates, and survival. However, the consequences of these effects on predator–prey interactions remain poorly understood. We examined how increased temperatures (30, 32, 34 °C) and the presence of water-borne predation cues from blue crabs (Callinectes sapidus) affected the morphology and growth rate of southern ribbed mussels (Geukensia granosissima), as well as their handling times when attacked by predatory crabs. Although southern ribbed mussels were able to survive under chronic heat stress, exposure to higher temperatures resulted in more elongated shell shapes. Growth rates in mussel wet weight were higher for mussels reared in the presence of a predator than in the predator-free control, but only in the low-temperature treatment. Likewise, handling times were greater for crabs eating mussels grown in the presence of a predator, but the effect was lost at the mid- and high-temperature treatments. These findings suggest that predation-induced defenses were suppressed when prey were under chronic thermal stress, which could make mussels more vulnerable to predation. The presence of predation cues in natural environments should be taken in consideration when estimating or predicting the effects of climate change on organisms.

Chemosensory cues of predators and competitors influence search for refuge in fruit by the coconut mite Aceria guerreronis.

Organisms are adapted to recognize environmental cues that can provide information about predation risk or competition. Non-vagrant eriophyoid mites mainly avoid predation by using habitats that are difficult for predators to access (galls or confined spaces in plants) such as the meristematic region of the coconut fruit, which is inhabited by the phytophagous mites Aceria guerreronis and Steneotarsonemus concavuscutum. The objective of this study was to investigate the response of A. guerreronis to cues from the predators Neoseiulus baraki and Amblyseius largoensis in coconut fruits, cues from conspecifics (A. guerreronis injured) and cues from the phytophage S. concavuscutum. The test was carried out through the release of about 300 A. guerreronis on coconut fruits previously treated with cues from predators, conspecific or heterospecific phytophagous. We also observed the walking behaviour of A. guerreronis exposed to the same chemical cues using a video tracking system. The infestation of fruits by A. guerreronis was greater in the presence of predator cues and reduced in the presence of S. concavuscutum cues, but cues from injured conspecifics did not interfere in the infestation process. In addition, the cues also altered the walking parameters of A. guerreronis: it walked more in response to cues from predators and the heterospecific phytophage. Aceria guerreronis spent more time in activity in the treatments with clues than in the control treatment. These results suggest that A. guerreronis recognizes cues from predators and competitors and modifies its behaviour to increase its fitness.

Predation cues influence metabolic rate and sensitivity to other chemical stressors in fathead minnows (Pimephales promelas) and Daphnia pulex.

The response of aquatic species to contaminants is often context dependent as illustrated by the influence that predation cues can have on the toxicity of some chemicals. We sought to gain additional insight into this interaction by examining how predation cues (alarm cue and fish kairomone) influence metabolic rate and the acute toxicity of sodium chloride and cadmium to fathead minnow larvae (Pimephales promelas) and sodium chloride to Daphnia pulex neonates. Consistent with a "flight or fight" response, the metabolic rate of fish larvae was elevated in the presence of alarm cue and growth of the minnows was also significantly reduced when exposed to alarm cue. The average 48-h LC50 for fathead minnows exposed to sodium chloride was significantly lower in the presence of alarm cue and kairomone combined as compared to tests with the salt alone. Analysis of the dose and survival response indicated alarm cue increased sensitivity of the fish to mid-range salt concentrations in particular. These results suggest an energetic cost of exposure to predation cues that resulted in enhanced toxicity of NaCl. Exposure to kairomone alone had no significant effect on salt toxicity to the minnows, which could be related to a lack of previous exposure to that cue. The acute toxicity of cadmium to the fish larvae was also not affected by the presence of predation cues which could be due to a metal-induced sensory system dysfunction or reduced bioavailability of the metal due to organic exudates from the predation cues. In contrast to the fathead minnow results, the metabolic rate of D. pulex and toxicity of NaCl to the daphnids were reduced in the presence of certain predator kairomones. This suggests an anti-predator response that enhanced tolerance to the salt. This study illustrates that the effect of predation cues on toxicity of aquatic contaminants can vary significantly based on the prey species, type of cue, and chemical stressor.

Embryonic exposure to a conspecific alarm cue triggers behavioural plasticity in juvenile rainbow trout

In fish, the presence of predator cues in the parental or juvenile environment engenders plasticity in the expression of fear-related behaviours. Whether these cues may engender developmental plasticity when they are present in the environment of embryos remains unexplored. Here, we tested in rainbow trout, Oncorhynchus mykiss : (1) whether exposure to alarm cues during embryonic stages engendered developmental plasticity; and (2) whether an abiotic stressor could also orient the behavioural development of fry. We divided fertilized eggs into three groups: a control nonstressed group (Control), a group of embryos exposed to a conspecific alarm pheromone (e.g. predator-related cue stressor, PS), and a group of embryos that were chronically air exposed for 1 min (e.g. abiotic stressor, AS). Stressors were applied once a day, 3 times per week from 19 days postfertilization (dpf) until 52 dpf. Between 57 and 143 dpf, and for each individual, we assessed the propensity to express fear responses in different contexts and learning performances. When exposed to a novel environment or a novel object, PS fish showed significantly less fear-related behaviour, less freezing and higher activity levels than Control fish. PS fish also showed slower acquisition of a learning task than controls. AS fish did not differ from controls in any test situation. Our results show that in ovo exposure to a natural but not an abiotic signal is a prominent inducer of rainbow trout behavioural plasticity across a number of contexts. Our study provides evidence that the expression of neophobia by fish fry may be modulated by the level of risk perceived by embryos in the environment.

Integrating trait multidimensionality, predation and autotomy to explain the maintenance of boldness

There is an ongoing debate on how personality types are maintained within populations. We tested, for the first time, the potential of trait multidimensionality and trait compensation, where prey compensate for the costs of one trait by relying more on another one, in maintaining variation in boldness within a population. We studied how four boldness-related traits and swimming escape performance covary and shape the probability of survival and autotomy of Ischnura pumilio damselfly larvae in an experiment with predatory dragonfly larvae. Our results did not support the common belief that bold individuals are selected against in terms of survival selection by predation. Instead, we found survival selection favouring individuals combining being bold for two boldness-related traits. The four boldness-related traits did not covary frequently, supporting the multidimensionality of boldness. Moreover, animals bolder for one trait (activity in the presence of predator cues) were shyer for another trait (response to predator cues), which indicated trait compensation. However, the support for trait compensation was limited. The only other case of trait compensation was that bold larvae compensated for their increased risk-taking behaviour in the presence of a predator with a higher probability of autotomy. These patterns may contribute to maintaining variation in boldness in damselfly populations. Just as boldness-related traits are multidimensional, the mechanisms underlying their persistence in natural populations are also likely to be multifaceted.

Contrasting gene expression programs correspond with predator-induced phenotypic plasticity within and across generations in Daphnia.

Research has shown that a change in environmental conditions can alter the expression of traits during development (i.e., "within-generation phenotypic plasticity") as well as induce heritable phenotypic responses that persist for multiple generations (i.e., "transgenerational plasticity", TGP). It has long been assumed that shifts in gene expression are tightly linked to observed trait responses at the phenotypic level. Yet, the manner in which organisms couple within- and TGP at the molecular level is unclear. Here we tested the influence of fish predator chemical cues on patterns of gene expression within- and across generations using a clone of Daphnia ambigua that is known to exhibit strong TGP but weak within-generation plasticity. Daphnia were reared in the presence of predator cues in generation 1, and shifts in gene expression were tracked across two additional asexual experimental generations that lacked exposure to predator cues. Initial exposure to predator cues in generation 1 was linked to ~50 responsive genes, but such shifts were 3-4× larger in later generations. Differentially expressed genes included those involved in reproduction, exoskeleton structure and digestion; major shifts in expression of genes encoding ribosomal proteins were also identified. Furthermore, shifts within the first-generation and transgenerational shifts in gene expression were largely distinct in terms of the genes that were differentially expressed. Such results argue that the gene expression programmes involved in within- vs. transgeneration plasticity are fundamentally different. Our study provides new key insights into the plasticity of gene expression and how it relates to phenotypic plasticity in nature.

Habitat quality mediates personality through differences in social context.

Assessing the stability of animal personalities has become a major goal of behavioral ecologists. Most personality studies have utilized solitary individuals, but little is known on the extent that individuals retain their personality across ecologically relevant group settings. We conducted a field survey which determined that mud crabs, Panopeus herbstii, remain scattered as isolated individuals on degraded oyster reefs while high quality reefs can sustain high crab densities (>10m-2). We examined the impact of these differences in social context on personality by quantifying the boldness of the same individual crabs when in isolation and in natural cohorts. Crabs were also exposed to either a treatment of predator cues or a control of no cue throughout the experiment to assess the strength of this behavioral reaction norm. Crabs were significantly bolder when in groups than as solitary individuals with predator cue treatments exhibiting severally reduced crab activity levels in comparison to corresponding treatments with no predator cues. Behavioral plasticity depended on the individual and was strongest in the presence of predator cues. While bold crabs largely maintained their personality in isolation and group settings, shy crabs would become substantially bolder when among conspecifics. These results imply that the shifts in crab boldness were a response to changes in perceived predation risk, and provide a mechanism for explaining variation in behavioral plasticity. Such findings suggest that habitat degradation may produce subpopulations with different behavioral patterns because of differing social interactions between individual animals.

Chlorpyrifos-induced oxidative damage is reduced under warming and predation risk: Explaining antagonistic interactions with a pesticide

Interactions with pollutants and environmental factors are poorly studied for physiological traits. Yet physiological traits are important for explaining and predicting interactions at higher levels of organization. We investigated the single and combined impact of the pesticide chlorpyrifos, predation risk and warming on endpoints related to oxidative stress in the damselfly Enallagma cyathigerum. We thereby integrated information on reactive oxygen species (ROS), antioxidant enzymes and oxidative damage. All three treatments impacted the oxidative stress levels and for most traits the pesticide interacted antagonistically with warming or predation risk. Chlorpyrifos exposure resulted in increased ROS levels, decreased antioxidant defence and increased oxidative damage compared to the control situation. Under warming, the pesticide-induced increase in oxidative stress was less strong and the investment in antioxidant defence higher. Although both the pesticide and predation risk increased oxidative damage, the effects of the pesticide on oxidative damage were less strong in the presence of predator cues (at 20 °C). Despite the weaker pesticide-induced effects under predation risk, the combination of the pesticide and predator cues consistently caused the highest ROS levels, the lowest antioxidant defence and the highest oxidative damage, indicating the importance of cumulative stressor effects for impairing fitness. Our results provide the first evidence for antagonistic interactions of warming and predation risk with a pollutant for physiological traits. We identified two general mechanisms that may generate antagonistic interactions for oxidative stress: cross-tolerance and the maximum cumulative levels of damage.

Pigmentation plasticity enhances crypsis in larval newts: associated metabolic cost and background choice behaviour

In heterogeneous environments, the capacity for colour change can be a valuable adaptation enhancing crypsis against predators. Alternatively, organisms might achieve concealment by evolving preferences for backgrounds that match their visual traits, thus avoiding the costs of plasticity. Here we examined the degree of plasticity in pigmentation of newt larvae (Lissotriton boscai) in relation to predation risk. Furthermore, we tested for associated metabolic costs and pigmentation-dependent background choice behaviour. Newt larvae expressed substantial changes in pigmentation so that light, high-reflecting environment induced depigmentation whereas dark, low-reflecting environment induced pigmentation in just three days of exposure. Induced pigmentation was completely reversible upon switching microhabitats. Predator cues, however, did not enhance cryptic phenotypes, suggesting that environmental albedo induces changes in pigmentation improving concealment regardless of the perceived predation risk. Metabolic rate was higher in heavily pigmented individuals from dark environments, indicating a high energetic requirement of pigmentation that could impose a constraint to larval camouflage in dim habitats. Finally, we found partial evidence for larvae selecting backgrounds matching their induced phenotypes. However, in the presence of predator cues, larvae increased the time spent in light environments, which may reflect a escape response towards shallow waters rather than an attempt at increasing crypsis.

Stoichiometric Responses to an Agricultural Pesticide Are Modified by Predator Cues.

Current ecological risk assessment of pesticides fails to protect aquatic ecosystem health. To get better insight in how pesticides may affect aquatic ecosystems, we tested how sublethal pesticide concentrations modify body stoichiometry. Moreover, as interactions with natural stressors may cause underestimates of the impact of pesticides, we also tested whether this pathway depended on the presence of predator cues. Therefore, we exposed damselfly larvae to chlorpyrifos and cues from predatory dragonflies and focused on body stoichiometry and associated explanatory variables (growth rate, RNA:DNA, and energy storage molecules). The way the predator cues modulated the pesticide effects strongly differed between endpoints. Exposure to chlorpyrifos affected the key body stoichiometric ratios: chlorpyrifos consistently increased N:P, while its effects on C:N (decrease with predator cues) and C:P (increase without predator cues) strongly depended upon the presence of the natural stressor. These stoichiometric responses could be explained by associated changes in growth, RNA:DNA, and in C-rich fat and sugars and N-rich proteins. The observed changes in body stoichiometry may affect the damselflies' food quality and have the potential to cascade through the food web and shape nutrient cycling.

Different Morphological Traits Influence Predator Defense and Space Use inPhysaacuta

Abstract: Individuals can respond to predation risk by building morphological defenses or by altering their behavior. We tested whether freshwater Physa acuta (Draparnaud, 1805) snails with better morphological defenses against predation risk displayed lower or higher behavioral responses to predator cues compared to more poorly defended snails. We examined how the morphological traits of snails influence their risk of predation by crayfish, inferred by crush resistance, and how those same traits also influence their patch use in the absence and presence of predator cues. Using model selection, we found that a large shell width increased crush resistance. We also found that other morphological traits interacted with predator cues to influence the use of high resource patches, however shell width had almost no influence. Aperture length and aperture width both strongly interacted with cue: larger aperture length and larger aperture width snails decreased their use of the high resource patch substantially. ...

Comparable cross-taxa risk perception by means of chemical cues in marine and freshwater crustaceans

Rapid identification of predation risk and modification of subsequent behaviour is essential for prey survival. In low-visibility aquatic environments, chemical cues emitted by hetero- and conspecific organisms may be an important information source if they identify risk or alternatively, indicate safety or resource availability. This study tested whether ecologically similar shrimp from disparate habitats have a comparable ability to identify predators from a range of taxa based on chemical cues. Shrimp from both temperate marine (Palaemon affinis) and tropical freshwater habitats (Caridina typus) exhibited similar behavioural responses, avoiding chemical cues from predatory heterospecifics, showing no response to non-predatory heterospecific cues, and preferring conspecific cues. These chemical cues also affected habitat selection, with structurally complex microhabitats favoured in the presence of predator cues but avoided in the presence of conspecific cues. The ability to differentiate predators from non-predators irrespective of taxa suggests identification might be due to the predator’s diet. An ability to alter behaviour based on vision-independent perception of ambient risk is likely to reduce capture risk while allowing individuals to maximise time spent on essential processes such as foraging.

Predator-prey interactions mediated by prey personality and predator hunting mode.

Predator-prey interactions are important drivers in structuring ecological communities. However, despite widespread acknowledgement that individual behaviours and predator species regulate ecological processes, studies have yet to incorporate individual behavioural variations in a multipredator system. We quantified a prevalent predator avoidance behaviour to examine the simultaneous roles of prey personality and predator hunting mode in governing predator-prey interactions. Mud crabs, Panopeus herbstii, reduce their activity levels and increase their refuge use in the presence of predator cues. We measured mud crab mortality and consistent individual variations in the strength of this predator avoidance behaviour in the presence of predatory blue crabs, Callinectes sapidus, and toadfish, Opsanus tau We found that prey personality and predator species significantly interacted to affect mortality with blue crabs primarily consuming bold mud crabs and toadfish preferentially selecting shy crabs. Additionally, the strength of the predator avoidance behaviour depended upon the predation risk from the predator species. Consequently, the personality composition of populations and predator hunting mode may be valuable predictors of both direct and indirect predator-prey interaction strength. These findings support theories postulating mechanisms for maintaining intraspecies diversity and have broad implications for community dynamics.

Cautious versus desperado males: predation risk affects courtship intensity but not female choice in a wolf spider

Understanding the decisions that animals make in the presence of predation risk can reveal their assessment of current and future reproductive options. The wolf spider, Pardosa milvina, has a conspicuous courtship display that is an indicator of male quality. In an initial experiment, we determined that male courtship was highly repeatable and correlated with symmetry. We then used symmetry as an indicator of quality to explore the reactions of males when presented with simulated predation risk and an attractive virgin female. There were no differences in courtship features between risk and no risk treatments unless we took into account male quality. High-quality males reduced courtship intensity under risk conditions suggesting that they estimated their long-term fitness prospects as strong. This response is consistent with the asset protection principle, which suggests that animals with high value traits should behave cautiously. Low-quality males courted at high levels under predation risk, which seemed to be reckless attempts to attract females. This response is analogous to the effect, which is one explanation for vigorous fighting by inferior animals in contests. Although females used behavior to select males when no predator information was present, they seemed to use symmetry in the presence of predator cues. The ability of females to select the most attractive males suggests that they can accurately assess male quality under laboratory conditions. High courting desperado males may occasionally be selected in more complex environments and/or when they are in competition with other males.

Activity level and aggregation behavior in the crustacean gammarid Gammarus insensibilis parasitized by the manipulative trematode Microphallus papillorobustus

Hosts manipulated by parasites are profoundly altered organisms exhibiting a broad range of potential modifications. Exploring this multidimensionality is an emerging field. Previous studies have shown that the bird trematode Microphallus papillorobustus induces several behavioural changes in the gammarid Gammarus insensibilis. Knowing that aggregation behaviour and reduced activity levels are strategies that limit predation in other species of amphipods, we explored in this study these behavioural responses for infected and uninfected G. insensibilis in the presence of host and non-host predator olfactory cues (bird faeces and fish mucus). While uninfected individuals reduced their activity level in the presence of predator cues, infected individuals did not change their activity level in presence of aquatic bird faeces. We also studied the gammarid aggregation behaviour. Uninfected gammarids in clean water spent significantly more time in aggregates than did infected individuals. Among the uninfected individuals, the aggregation level tended to increase when bird faeces and fish mucus were added, but the difference was not significant. Among infected individuals, the level of aggregation was significantly increased only with the bird faeces. We discussed our results in the context of the literature on multidimensional manipulations, acknowledging that subtle differences between unparasitized and parasitized gammarids can also be by-products of manipulation on other traits.

Divergent phenotypic responses to predators and cyanobacteria inDaphnia lumholtzi

Daphnia lumholtzi is an exotic species of zooplankton that was first introduced in Texas, U.S.A., and has since spread across most of the areas in the country. Research has focussed on the importance of the production of morphological defences in response to predator exposure as a key explanation for the spread of this species. Very little is known about the influence of other common environmental stressors on the fitness of this species or the potential role for genetic variation in plasticity in the spread of this species. We assessed the effects of two common environmental stressors, invertebrate predator cues and increasing concentrations of cyanobacteria, on the life-history traits in D. lumholtzi. This study also included clones from three reservoirs in Texas to measure potential genetic variation in plasticity. We found that the expression of life-history traits depended strongly upon the combined effects of predator exposure and food quality. Increasing concentrations of cyanobacteria resulted in delayed maturation, slower growth, a smaller size at maturation, declines in clutch size and slower rate of population growth. Yet, such declines were much smaller in the presence of predator cues. Divergent responses observed were the size of defence traits; Daphnia reared in the absence of predator cues increased the size of spines as the concentrations of cyanobacteria increased, while the opposite pattern was observed in the presence of predator cues. This study also revealed extensive genetic variation in the magnitude and direction of phenotypic responses to predators and cyanobacteria. These latter results illustrate that significant clonal variation in plasticity may help promote the spread of this species.