Variation in anti-predator behavior among five strains of inbred guppies, Poecilia reticulata

The pharmaceutical pollutant fluoxetine alters reproductive behaviour in a fish independent of predation risk

Pharmaceutical pollutants constitute a major threat to wildlife because of their capacity to induce biological effects at low doses. One such pollutant is the antidepressant fluoxetine, which has been detected in surface waters globally at levels that recent studies suggest can alter physiology and behaviour in aquatic organisms. However, wildlife exposed to pharmaceutical contaminants are typically confronted with multiple stressors simultaneously, including predation risk, which is a particularly important natural stressor that can have direct (e.g. mortality) and indirect (e.g. changed prey behaviour) fitness effects. Accordingly, we investigated potential impacts of environmentally realistic fluoxetine exposure on reproductive behaviour in the guppy (Poecilia reticulata) under predation risk. Specifically, we tested whether fluoxetine exposure altered mating behaviour in male and female guppies in the presence of either a predatory spangled perch (Leiopotherapon unicolor) or a non-predatory rainbowfish (Melanotaenia splendida) control. We found that fluoxetine and the presence of a predatory spangled perch did not interact to affect reproductive behaviour. We also found that, independent of a predatory threat, fluoxetine exposure altered male mating strategy, with males in the high treatment conducting significantly more coercive 'sneak' copulations, whereas the number of courtship displays performed was not significantly affected. Moreover, while fluoxetine exposure did not significantly affect the amount of time that males and females spent following one another, we found that females, but not males, followed a potential partner less when in the presence of the predatory fish. Finally, both sexes reacted to the risk of predation by spending less time in close proximity to a predator than a non-predator. In combination, our findings highlight the capacity of fluoxetine to influence processes of sexual selection at field-realistic concentrations and emphasise the importance of considering multiple stressors when assessing impacts of pharmaceutical pollutants on the behaviour of wildlife.

Testing the stability of behavioural coping style across stress contexts in the Trinidadian guppy

Within populations, individuals can vary in stress response, a multivariate phenomenon comprising neuroendocrine, physiological and behavioural traits.Verbal models of individual stress "coping style" have proposed that the behavioural component of this variation can be described as a single axis, with each individual's coping style being consistent across time and stress contexts.Focusing on this behavioural component of stress response and combining repeated measures of multiple traits with a novel multivariate modelling framework, we test for the existence of coping style variation and assess its stability across contexts in the Trinidadian guppy (Poecilia reticulata).Specifically, we test the following hypotheses: (1) there exists repeatable among-individual behavioural (co)variation ("personality") within a mild stress context consistent with a risk-averse-risk-prone continuum of behavioural coping style, (2) there is population-level plasticity in behaviour as a function of stressor severity, (3) there is among-individual variation in plasticity (i.e. IxE), and (4) the presence of IxE reduces cross-context stability of behavioural coping style.We found significant repeatable among-individual behavioural (co)variation in the mild stress context (open field trial), represented as an I matrix. However, I was not readily described by a simple risk-averse-risk-prone continuum as posited by the original coping style model. We also found strong evidence for population-level changes in mean behaviour with increasing stressor severity (simulated avian and piscine predation risks).Single-trait analyses did show the presence of individual-by-environment interactions (IxE), as among-individual cross-context correlations were significantly less than +1. However, multitrait analysis revealed the consequences of this plasticity variation were minimal. Specifically, we found little evidence for changes in the structure of I between mild and moderate stress contexts overall, and only minor changes between the two moderate contexts (avian vs. piscine predator).We show that a multivariate approach to assessing changes in among-individual (co)variance across contexts can prevent the over-interpretation of statistically significant, but small, individual-by-environment effects. While behavioural flexibility enables populations (and individuals) to respond rapidly to changes in the environment, multivariate personality structure can be conserved strongly across such contexts. A plain language summary is available for this article.

Telomere length reveals cumulative individual and transgenerational inbreeding effects in a passerine bird

Inbreeding results in more homozygous offspring that should suffer reduced fitness, but it can be difficult to quantify these costs for several reasons. First, inbreeding depression may vary with ecological or physiological stress and only be detectable over long time periods. Second, parental homozygosity may indirectly affect offspring fitness, thus confounding analyses that consider offspring homozygosity alone. Finally, measurement of inbreeding coefficients, survival and reproductive success may often be too crude to detect inbreeding costs in wild populations. Telomere length provides a more precise measure of somatic costs, predicts survival in many species and should reflect differences in somatic condition that result from varying ability to cope with environmental stressors. We studied relative telomere length in a wild population of Seychelles warblers (Acrocephalus sechellensis) to assess the lifelong relationship between individual homozygosity, which reflects genome‐wide inbreeding in this species, and telomere length. In juveniles, individual homozygosity was negatively associated with telomere length in poor seasons. In adults, individual homozygosity was consistently negatively related to telomere length, suggesting the accumulation of inbreeding depression during life. Maternal homozygosity also negatively predicted offspring telomere length. Our results show that somatic inbreeding costs are environmentally dependent at certain life stages but may accumulate throughout life.

The evolution of antipredator behaviour following relaxed and reversed selection in Alaskan threespine stickleback fish

Changing environments, whether through natural or anthropogenic causes, can lead to the loss of some selective pressures ('relaxed selection') and possibly even the reinstatement of selective agents not encountered for many generations ('reversed selection'). We examined the outcome of relaxed and reversed selection in the adaptive radiation of the threespine stickleback fish, Gasterostues aculeatus L., in which isolated populations encounter a variety of predation regimes. Oceanic stickleback, which represent the ancestral founders of the freshwater radiation, encounter many piscivorous fish. Derived, freshwater populations, on the other hand, vary with respect to the presence of predators. Some populations encounter native salmonids, whereas others have not experienced predation by large fish in thousands of generations (relax-selected populations). Some relax-selected populations have had sport fish, including rainbow trout, Oncorhynchus mykiss, introduced within the past several decades (reverse-selected). We examined the behavioural responses of stickleback from three populations of each type to simulated attacks by trout and birds to determine whether relaxed and reversed selection has led to divergence in behaviour, and whether this divergence was predator specific. Fish from trout-free populations showed weak responses to trout, as predicted, but these responses were similar to those of oceanic (ancestral) populations. Fish from populations that co-occur with trout, whether native or introduced, showed elevated antipredator responses, indicating that in freshwater, trout predation selects for enhanced antipredator responses, which can evolve extremely rapidly. Comparison of laboratory-reared and wild-caught individuals suggests a combination of learned and genetic components to this variation. Responses to a model bird flyover were weakly linked to predation environment, indicating that the loss of predation by trout may partially influence the evolution of responses to birds. Our results reject the hypothesis that the consistent presence of predatory birds has been sufficient to maintain responses to piscivorous fish under periods of relaxed selection.

A tale of two contribution mechanisms for nonlinear public goods

Amounts of empirical evidence, ranging from microbial cooperation to collective hunting, suggests public goods produced often nonlinearly depend on the total amount of contribution. The implication of such nonlinear public goods for the evolution of cooperation is not well understood. There is also little attention paid to the divisibility nature of individual contribution amount, divisible vs. non-divisible ones. The corresponding strategy space in the former is described by a continuous investment while in the latter by a continuous probability to contribute all or nothing. Here, we use adaptive dynamics in finite populations to quantify and compare the roles nonlinearity of public-goods production plays in cooperation between these two contribution mechanisms. Although under both contribution mechanisms the population can converge into a coexistence equilibrium with an intermediate cooperation level, the branching phenomenon only occurs in the divisible contribution mechanism. The results shed insight into understanding observed individual difference in cooperative behavior.

Three-dimensional neurophenotyping of adult zebrafish behavior

The use of adult zebrafish (Danio rerio) in neurobehavioral research is rapidly expanding. The present large-scale study applied the newest video-tracking and data-mining technologies to further examine zebrafish anxiety-like phenotypes. Here, we generated temporal and spatial three-dimensional (3D) reconstructions of zebrafish locomotion, globally assessed behavioral profiles evoked by several anxiogenic and anxiolytic manipulations, mapped individual endpoints to 3D reconstructions, and performed cluster analysis to reconfirm behavioral correlates of high- and low-anxiety states. The application of 3D swim path reconstructions consolidates behavioral data (while increasing data density) and provides a novel way to examine and represent zebrafish behavior. It also enables rapid optimization of video tracking settings to improve quantification of automated parameters, and suggests that spatiotemporal organization of zebrafish swimming activity can be affected by various experimental manipulations in a manner predicted by their anxiolytic or anxiogenic nature. Our approach markedly enhances the power of zebrafish behavioral analyses, providing innovative framework for high-throughput 3D phenotyping of adult zebrafish behavior.

Evolutionary causes and consequences of consistent individual variation in cooperative behaviour

Behaviour is typically regarded as among the most flexible of animal phenotypic traits. In particular, expression of cooperative behaviour is often assumed to be conditional upon the behaviours of others. This flexibility is a key component of many hypothesized mechanisms favouring the evolution of cooperative behaviour. However, evidence shows that cooperative behaviours are often less flexible than expected and that, in many species, individuals show consistent differences in the amount and type of cooperative and non-cooperative behaviours displayed. This phenomenon is known as 'animal personality' or a 'behavioural syndrome'. Animal personality is evolutionarily relevant, as it typically shows heritable variation and can entail fitness consequences, and hence, is subject to evolutionary change. Here, we review the empirical evidence for individual variation in cooperative behaviour across taxa, we examine the evolutionary processes that have been invoked to explain the existence of individual variation in cooperative behaviour and we discuss the consequences of consistent individual differences on the evolutionary stability of cooperation. We highlight that consistent individual variation in cooperativeness can both stabilize or disrupt cooperation in populations. We conclude that recognizing the existence of consistent individual differences in cooperativeness is essential for an understanding of the evolution and prevalence of cooperation.

Scototaxis as anxiety-like behavior in fish

The scototaxis (dark/light preference) protocol is a behavioral model for fish that is being validated to assess the antianxiety effects of pharmacological agents and the behavioral effects of toxic substances, and to investigate the (epi)genetic bases of anxiety-related behavior. Briefly, a fish is placed in a central compartment of a half-black, half-white tank; following habituation, the fish is allowed to explore the tank for 15 min; the number and duration of entries in each compartment (white or black) are recorded by the observer for the whole session. Zebrafish, goldfish, guppies and tilapias (all species that are important in behavioral neurosciences and neuroethology) have been shown to demonstrate a marked preference for the dark compartment. An increase in white compartment activity (duration and/or entries) should reflect antianxiety behavior, whereas an increase in dark compartment activity should reflect anxiety-promoting behavior. When individual animals are exposed to the apparatus on only one occasion, results can be obtained in 20 min per fish.

Indirect genetic effects influence antipredator behavior in guppies: estimates of the coefficient of interaction psi and the inheritance of reciprocity

How and why cooperation evolves, particularly among nonrelatives, remains a major paradox for evolutionary biologists and behavioral ecologists. Although much attention has focused on fitness consequences associated with cooperating, relatively little is known about the second component of evolutionary change, the inheritance of cooperation or reciprocity. The genetics of behaviors that can only be expressed in the context of interactions are particularly difficult to describe because the relevant genes reside in multiple social partners. Indirect genetic effects (IGEs) describe the influence of genes carried in social partners on the phenotype of a focal individual and thus provide a novel approach to quantifying the genetics underlying interactions such as reciprocal cooperation. We used inbred lines of guppies and a novel application of IGE theory to describe the dual genetic control of predator inspection and social behavior, both classic models of reciprocity. We identified effects of focal strain, social group strain, and interactions between focal and group strains on variation in focal behavior. We measured psi, the coefficient of the interaction, which describes the degree to which an individual's phenotype is influenced by the phenotype of its social partners. The genetic identity of social partners substantially influences inspection behavior, measures of threat assessment, and schooling and does so in positively reinforcing manner. We therefore demonstrate strong IGEs for antipredator behavior that represent the genetic variation necessary for the evolution of reciprocity.

Are designer guppies inbred? Microsatellite variation in five strains of ornamental guppies, Poecilia reticulata, used for behavioral research

Inbred lines are an important tool of genetic studies of all traits, including behavior. Independently derived strains of ornamental "designer" guppies are readily available and predicted to be inbred; however, little is known about actual levels of inbreeding in any of these strains or whether these lines differ in genetic traits that have not been under strong directional artificial selection. We genotyped five designer strains of guppies known to vary in their responses to predator cues and a wild reference population to determine whether designer strains show evidence of inbreeding and whether the strains differed from each other at five microsatellite loci. The designer strains exhibited lower allelic diversity and observed heterozygosity than the wild population. Observed heterozygosity departed significantly from expected heterozygosity for most markers in all five strains of designer guppies. Inbreeding coefficient (f) comparisons between the wild reference population and the designer strains show considerable inbreeding in the designer strains. F(is) values for the designer strains also provide evidence of inbreeding. Finally, F(st) values indicate that the designer strains differ significantly from each other and the wild population. We therefore concluded that designer guppies are inbred compared to wild populations and differ among strains, making them useful tools for genetic studies of behavioral or life history traits.

Nonadditive effects of group membership can lead to additive group phenotypes for anti-predator behaviour of guppies, Poecilia reticulata

Nonadditive effects of group membership are generated when individuals respond differently to the same social environment and may alter predictions about how behavioural evolution will occur. Despite this importance, the relationship between an individual's behaviour in two different social contexts and how reciprocal interactions among individuals within groups influence group behaviour are poorly understood. Guppy anti-predator behaviour can be used to explore how individuals behaviourally respond to changes in social context. Individuals from two strains were tested for response to a model predator alone and in groups to evaluate how individuals alter their behaviour in response to social context and how group phenotype relates to individual behaviour. Nonadditive effects of group membership were detected for a number of behaviours, revealing that the effect of being in a group differed among individuals. These nonadditive effects, however, yielded an additive group phenotype. That is, the average behaviour of the group was equal to the average of its parts, for all behaviours in both strains. Such an additive group phenotype may have resulted because all individuals within a group respond to the specific social environment provided by the other members of their group.

Zebrafish (Danio rerio) responds differentially to stimulus fish: the effects of sympatric and allopatric predators and harmless fish

The zebrafish has been an excellent model organism of developmental biology and genetics. Studying its behavior will add to the already strong knowledge of its biology and will strengthen the use of this species in behavior genetics and neuroscience. Anxiety is one of the most problematic human psychiatric conditions. Arguably, it arises as a result of abnormally exaggerated natural fear responses. The zebrafish may be an appropriate model to investigate the biology of fear and anxiety. Fear responses are expressed by animals when exposed to predators, and these responses can be learned or innate. Here we investigated whether zebrafish respond differentially to a natural predator or other fish species upon their first exposure to these fish. Naïve zebrafish were shown four species of fish chosen based on predatory status (predatory or harmless) and geographical origin (allopatric or sympatric). Our results suggest that naïve zebrafish respond differentially to the stimulus fish. Particularly interesting is the antipredatory response elicited by the zebrafish's sympatric predator, the Indian Leaf Fish, and the fact that this latter species exhibited almost no predatory attacks. The findings obtained open a new avenue of research into what zebrafish perceive as "dangerous" or fear inducing. They will also allow us to develop fear and anxiety related behavioral test methods with which the contribution of genes to, or the effects of novel anxiolytic substances on these behaviors may be analyzed.