Individual experience and evolutionary history of predation affect expression of heritable variation in fish personality and morphology

Sociability in Fruit Flies: Genetic Variation, Heritability and Plasticity

Sociability, defined as individuals' propensity to participate in non-aggressive activities with conspecifics, is a fundamental feature of behavior in many animals including humans. However, we still have a limited knowledge of the mechanisms and evolutionary biology of sociability. To enhance our understanding, we developed a new protocol to quantify sociability in fruit flies (Drosophila melanogaster). In a series of experiments with 59 F1 hybrids derived from inbred lines, we documented, first, significant genetic variation in sociability in both males and females, with broad-sense heritabilities of 0.24 and 0.21 respectively. Second, we observed little genetic correlation in sociability between the sexes. Third, we found genetic variation in social plasticity among the hybrids, with a broad-sense heritability of ~0.24. That is, genotypes differed in the degree of sociability after experiencing the same relevant social experience. Our data pave the way for further research on the mechanisms that underlie sociability as well as its ecological and evolutionary consequences.

Repeatable aversion across threat types is linked with life-history traits but is dependent on how aversion is measured

Personality research suggests that individual differences in risk aversion may be explained by links with life-history variation. However, few empirical studies examine whether repeatable differences in risk avoidance behaviour covary with life-history traits among individuals in natural populations, or how these links vary depending on the context and the way risk aversion is measured. We measured two different risk avoidance behaviours (latency to enter the nest and inspection time) in wild great tits (Parus major) in two different contexts-response to a novel object and to a predator cue placed at the nest-box during incubation---and related these behaviours to female reproductive success and condition. Females responded equally strongly to both stimuli, and although both behaviours were repeatable, they did not correlate. Latency to enter was negatively related to body condition and the number of offspring fledged. By contrast, inspection time was directly explained by whether incubating females had been flushed from the nest before the trial began. Thus, our inferences on the relationship between risk aversion and fitness depend on how risk aversion was measured. Our results highlight the limitations of drawing conclusions about the relevance of single measures of a personality trait such as risk aversion.

Personality and the retention of neophobic predator avoidance in wild caught Trinidadian guppies

Neophobic predator avoidance allows prey to reduce the risk of predation but is costly in terms of reduced foraging or courtship opportunities if the novel cues do not represent an actual threat. Consequently, neophobic responses to novel cues should wane with repeated exposures in the absence of an actual threat. We tested the prediction that individual personality traits shape the retention of neophobic predator avoidance in wild-caught guppies. Using extinction trials, we demonstrate that personality (measured as latency to escape or approach a novel object) did not influence the initial response of wild-caught Trinidadian guppies to a novel odour; bolder and shyer guppies both exhibited similarly strong avoidance responses. However, after several exposures, shyer guppies maintain an avoidance response, and bolder guppies no longer respond. Our results highlight the complex nature of the antipredator algorithm of prey, whereby past experience, acute risk, and individual tactics shape neophobic predator avoidance patterns.

Environment-dependence of behavioural consistency in adult male European green lizards (Lacerta viridis)

Understanding the background mechanisms affecting the emergence and maintenance of consistent between-individual variation within population in single (animal personality) or across multiple (behavioural syndrome) behaviours has key importance. State-dependence theory suggests that behaviour is ‘anchored’ to individual state (e.g. body condition, gender, age) and behavioural consistency emerges through behavioural-state feedbacks. A number of relevant state variables are labile (e.g. body condition, physiological performance) and expected to be affected by short-term environmental change. Yet, whether short-term environmental shifts affect behavioural consistency during adulthood remains questionable. Here, by employing a full-factorial laboratory experiment, we explored if quantity of food (low vs. high) and time available for thermoregulation (3h vs. 10h per day) had an effect on activity and risk-taking of reproductive adult male European green lizards (Lacerta viridis). We focussed on different components of behavioural variation: (i) strength of behavioural consistency (repeatability for animal personality; between-individual correlation for behavioural syndrome), (ii) behavioural type (individual mean behaviour) and (iii) behavioural predictability (within-individual behavioural variation). Activity was repeatable in all treatments. Risk-taking was repeatable only in the low basking treatments. We found significant between-individual correlation only in the low food × long basking time group. The treatments did not affect behavioural type, but affected behavioural predictability. Activity predictability was higher in the short basking treatment, where it also decreased with size (≈ age). Risk-taking predictability in the short basking treatment increased with size under food limitation, but decreased when food supply was high. We conclude that short-term environmental change can alter various components of behavioural consistency. The effect could be detected in the presence/absence patterns of animal personality and behavioural syndrome and the level of individual behavioural predictability, but not in behavioural type.

Divorce in an Island Bird Population: Causes, Consequences, and Lack of Inheritance

Divorce (mate switching) is widely considered an adaptive strategy that female birds use to improve their reproductive success. However, in few species are the causes and consequences of divorce well understood, and the genetic basis and inheritance of divorce have never been explored. In Savannah sparrows (Passerculus sandwichensis) breeding on Kent Island, New Brunswick, Canada, 47.0% of pairs in which both partners survived to the following breeding season ended in divorce. Secondary females, which received less parental assistance than primary females, tended to divorce when breeding success was low or when paired with small males. Unlike young females or widows, older females improved their fledging success after divorce. Young males (but not older males) suffered lower reproductive success following a divorce. However, neither the lifetime number of divorces nor whether an individual had ever divorced affected the fitness of females or males, which suggests little or no selection for the trait. We found moderate repeatability for divorce in females (although not in males) but no additive genetic variance or evidence of maternal or paternal effects. Divorce in Savannah sparrows appears to be a nonheritable flexible behavior whose expression and consequences depend on an individual's sex, mating status, size, and age.

Evolution of risk preference is determined by reproduction dynamics, life history, and population size

Alternative behavioral strategies typically differ in their associated risks, meaning that a different variance in fitness-related outcomes characterizes each behavior. Understanding how selection acts on risk preference is crucial to interpreting and predicting behavior. Despite much research, most theoretical frameworks have been laid out as optimization problems from the individual's perspective, and the influence of population dynamics has been underappreciated. We use agent-based simulations that implement competition between two simple behavioral strategies to illuminate effects of population dynamics on risk-taking. We explore the effects of inter-generational reproduction dynamics, population size, the number of decisions throughout an individual's life, and simple alternate distributions of risk. We find that these factors, very often ignored in empirical and theoretical studies of behavior, can have significant and non-intuitive impacts on the selection of alternative behavioral strategies. Our results demonstrate that simple rules regarding predicted risk preference do not hold across the complete range of each of the factors we studied; we propose intuitive interpretations for the dynamics within each regime. We suggest that studies of behavioral strategies should explicitly take into account the species' life history and the ecological context in which selection acted on the risk-related behavior of the organism of interest.

Predation risk and abiotic habitat parameters affect personality traits in extremophile populations of a neotropical fish (Poecilia vivipara)

Understanding whether and how ambient ecological conditions affect the distribution of personality types within and among populations lies at the heart of research on animal personality. Several studies have focussed on only one agent of divergent selection (or driver of plastic changes in behavior), considering either predation risk or a single abiotic ecological factor. Here, we investigated how an array of abiotic and biotic environmental factors simultaneously shape population differences in boldness, activity in an open‐field test, and sociability/shoaling in the livebearing fish Poecilia vivipara from six ecologically different lagoons in southeastern Brazil. We evaluated the relative contributions of variation in predation risk, water transparency/visibility, salinity (ranging from oligo‐ to hypersaline), and dissolved oxygen. We also investigated the role played by environmental factors for the emergence, strength, and direction of behavioral correlations. Water transparency explained most of the behavioral variation, whereby fish from lagoons with low water transparency were significantly shyer, less active, and shoaled less than fish living under clear water conditions. When we tested additional wild‐caught fish from the same lagoons after acclimating them to homogeneous laboratory conditions, population differences were largely absent, pointing toward behavioral plasticity as a mechanism underlying the observed behavioral differences. Furthermore, we found correlations between personality traits (behavioral syndromes) to vary substantially in strength and direction among populations, with no obvious associations with ecological factors (including predation risk). Altogether, our results suggest that various habitat parameters simultaneously shape the distribution of personality types, with abiotic factors playing a vital (as yet underestimated) role. Furthermore, while predation is often thought to lead to the emergence of behavioral syndromes, our data do not support this assumption.

Facing different predators: adaptiveness of behavioral and morphological traits under predation

Predation is thought to be one of the main structuring forces in animal communities. However, selective predation is often measured on isolated traits in response to a single predatory species, but only rarely are selective forces on several traits quantified or even compared between different predators naturally occurring in the same system. In the present study, we therefore measured behavioral and morphological traits in young-of-the-year Eurasian perch Perca fluviatilis and compared their selective values in response to the 2 most common predators, adult perch and pike Esox lucius. Using mixed effects models and model averaging to analyze our data, we quantified and compared the selectivity of the 2 predators on the different morphological and behavioral traits. We found that selection on the behavioral traits was higher than on morphological traits and perch predators preyed overall more selectively than pike predators. Pike tended to positively select shallow bodied and nonvigilant individuals (i.e. individuals not performing predator inspection). In contrast, perch predators selected mainly for bolder juvenile perch (i.e. individuals spending more time in the open, more active), which was most important. Our results are to the best of our knowledge the first that analyzed behavioral and morphological adaptations of juvenile perch facing 2 different predation strategies. We found that relative specific predation intensity for the divergent traits differed between the predators, providing some additional ideas why juvenile perch display such a high degree of phenotypic plasticity.

Predation environment affects boldness temperament of neotropical livebearers

Behavioral traits of individuals are important phenotypes that potentially interact with many other traits, an understanding of which may illuminate the evolutionary forces affecting populations and species. Among the five axes of temperament is the propensity to behave boldly in the presence of a perceived risk. To determine the effect of different predatorial regimes on boldness and fearfulness, we assessed the behavior of individuals in a novel portable swim chamber (i.e., forced open‐field test) by Brachyrhaphis rhabdophora (n = 633). We used an information theoretic framework to compare generalized (logistic) linear fixed‐effects models of predatorial regime (predator‐free [n = 6] and predator [n = 4] sites), sex, and standard length (SL). Fish from predator sites were much more fearful in the novel arena than fish from nonpredator sites. This varied by length, but not by sex. At 48 mm SL, fish from nonpredator sites were 4.9 times more likely to express bold behavior (ambulation) in the novel swim chamber as fish from predator sites. Probabilities of “ambulating” within the swim chamber increased with size for nonpredator sites and decreased with size for predator sites.

Behavioural responses to human-induced change: Why fishing should not be ignored

Change in behaviour is usually the first response to human‐induced environmental change and key for determining whether a species adapts to environmental change or becomes maladapted. Thus, understanding the behavioural response to human‐induced changes is crucial in the interplay between ecology, evolution, conservation and management. Yet the behavioural response to fishing activities has been largely ignored. We review studies contrasting how fish behaviour affects catch by passive (e.g., long lines, angling) versus active gears (e.g., trawls, seines). We show that fishing not only targets certain behaviours, but it leads to a multitrait response including behavioural, physiological and life‐history traits with population, community and ecosystem consequences. Fisheries‐driven change (plastic or evolutionary) of fish behaviour and its correlated traits could impact fish populations well beyond their survival per se, affecting predation risk, foraging behaviour, dispersal, parental care, etc., and hence numerous ecological issues including population dynamics and trophic cascades. In particular, we discuss implications of behavioural responses to fishing for fisheries management and population resilience. More research on these topics, however, is needed to draw general conclusions, and we suggest fruitful directions for future studies.

Fitness Consequences of Boldness in Juvenile and Adult Largemouth Bass

To date, most studies investigating the relationship between personality traits and fitness have focused on a single measure of fitness (such as survival) at a specific life stage. However, many personality traits likely have multiple effects on fitness, potentially operating across different functional contexts and stages of development. Here, we address the fitness consequences of boldness, under seminatural conditions, across life stages and functional contexts in largemouth bass (Micropterus salmoides). Specifically, we report the effect of boldness on (1) juvenile survivorship in an outdoor pond containing natural prey and predators and (2) adult reproductive success in three outdoor ponds across three reproductive seasons (years). Juvenile survival was negatively affected by boldness, with bolder juveniles having a lower probability of survival than shyer juveniles. In contrast, bolder adult male bass had greater reproductive success than their shyer male counterparts. Female reproductive success was not affected by boldness. These findings demonstrate that boldness can affect fitness differently across life stages. Further, boldness was highly consistent across years and significantly heritable, which suggests that boldness has a genetic component. Thus, our results support theory suggesting that fitness trade-offs across life stages may contribute to the maintenance of personality variation within populations.

You eat what you are: personality-dependent filial cannibalism in a fish with paternal care

Many animal parents invest heavily to ensure offspring survival, yet some eventually consume some or all of their very own young. This so‐called filial cannibalism is known from a wide range of taxa, but its adaptive benefit remains largely unclear. The extent to which parents cannibalize their broods varies substantially not only between species, but also between individuals, indicating that intrinsic behavioral differences, or animal personalities, might constitute a relevant proximate trigger for filial cannibalism. Using a marine fish with extensive paternal care, the common goby (Pomatoschistus microps), we investigated the influence of animal personality on filial cannibalism by assessing (1) behavioral consistency across a breeding and a nonbreeding context; (2) correlations between different breeding (egg fanning; filial cannibalism) and nonbreeding (activity) behaviors, and, in a separate experiment; (3) whether previously established personality scores affect filial cannibalism levels. We found consistent individual differences in activity across contexts. Partial filial cannibalism was independent of egg fanning but correlated strongly with activity, where active males cannibalized more eggs than less active males. This pattern was strong initially but vanished as the breeding season progressed. The incidence of whole clutch filial cannibalism increased with activity and clutch size. Our findings indicate that filial cannibalism cannot generally be adjusted independently of male personality and is thus phenotypically less plastic than typically assumed. The present work stresses the multidimensional interaction between animal personality, individual plasticity and the environment in shaping filial cannibalism.

Variation among free-living spotted hyenas in three personality traits

Inter-individual differences in behaviour, termed ‘animal personality’, are often consistent over time and across contexts and can be significantly related to fitness. However, most studies of animal personality are conducted in the laboratory or involve experimental protocols. Here, we used longitudinal scan and all-occurrence data collected under naturalistic conditions over 21 years to study boldness, aggressiveness, and sociability in a wild population of spotted hyenas (Crocuta crocuta). We found significant variation among individual hyenas in all three traits; however, whereas both sexes exhibited consistent inter-individual differences in aggressiveness and sociability, males were less consistent than females in their boldness. Heritability and maternal effects were small but significant for both boldness and sociability. A large proportion of the variation in aggressiveness could be attributed to genetic and maternal effects, supporting previous research linking hormone exposure in utero to aggressive behaviour later in life. All three traits were correlated with at least one measure of fitness. Particularly aggressive females were more successful in raising their offspring to reproductive maturity than less aggressive females. Interestingly, the reproductive benefits of sociability depended on social rank; for low-ranking hyenas, gaining feeding tolerance via sociability may significantly enhance reproductive success. Both boldness and sociability were linked to survival, but these traits affected longevity in different ways; highly social hyenas lived longer than those that were less social, but selection on boldness was stabilizing, favoring hyenas with intermediate boldness values that balance the benefits of risky behaviour against risks of injury and death.

No personality without experience? A test on Rana dalmatina tadpoles

While the number of studies reporting the presence of individual behavioral consistency (animal personality, behavioral syndrome) has boomed in the recent years, there is still much controversy about the proximate and ultimate mechanisms resulting in the phenomenon. For instance, direct environmental effects during ontogeny (phenotypic plasticity) as the proximate mechanism behind the emergence of consistent individual differences in behavior are usually overlooked compared to environmental effects operating across generations (genetic adaptation). Here, we tested the effects of sociality and perceived predation risk during ontogeny on the strength of behavioral consistency in agile frog (Rana dalmatina) tadpoles in a factorial common garden experiment. Tadpoles reared alone and without predatory cues showed zero repeatability within (i.e., lack of personality) and zero correlation between (i.e., lack of syndrome) activity and risk-taking. On the other hand, cues from predators alone induced both activity and risk-taking personalities, while cues from predators and conspecifics together resulted in an activity - risk-taking behavioral syndrome. Our results show that individual experience has an unequivocal role in the emergence of behavioral consistency. In this particular case, the development of behavioral consistency was most likely the result of genotype × environment interactions, or with other words, individual variation in behavioral plasticity.

Intraguild predation leads to genetically based character shifts in the threespine stickleback

Intraguild predation is a common ecological interaction that occurs when a species preys upon another species with which it competes. The interaction is potentially a mechanism of divergence between intraguild prey (IG-prey) populations, but it is unknown if cases of character shifts in IG-prey are an environmental or evolutionary response. We investigated the genetic basis and inducibility of character shifts in threespine stickleback from lakes with and without prickly sculpin, a benthic intraguild predator (IG-predator). Wild populations of stickleback sympatric with sculpin repeatedly show greater defensive armor and water column height preference. We laboratory-raised stickleback from lakes with and without sculpin, as well as marine stickleback, and found that differences between populations in armor, body shape, and behavior persisted in a common garden. Within the common garden, we raised stickleback half-families from multiple populations in the presence and absence of sculpin. Although the presence of sculpin induced trait changes in the marine stickleback, we did not observe an induced response in the freshwater stickleback. Behavioral and morphological trait differences between freshwater populations thus have a genetic basis and suggest an evolutionary response to intraguild predation.

Different behaviour-body length correlations in two populations of juvenile three-spined stickleback (Gasterosteus aculeatus)

Behavioural variation among individuals has received a lot of attention by behavioural ecologists in the past few years. Its causes and consequences are becoming vast areas of research. The origin and maintenance of individual variation in behaviour within and among populations is affected by many facets of the biotic and abiotic environment. Here, two populations of lab-reared juvenile three-spined sticklebacks (Gasterosteus aculeatus) are tested for three behaviours (boldness, exploration, and sociability). Given the identical rearing conditions, the only difference between these populations is the parental habitat. In both populations, correlations between behaviour and body length are found. Interestingly, these differ between the populations. In one population body length was negatively correlated with exploratory behaviour, while in the other one body length correlated negatively with sociability. Considering the identical environment these juvenile fish were exposed to, these findings suggest a potential (epi)genetic foundation for these correlations and shows that, in three-spined sticklebacks, the proximate basis for correlations between body length and behaviour appears quite malleable.

Effect of diet on the structure of animal personality

There is increasing interest in the proximate factors that underpin individual variation in suites of correlated behaviours. In this paper, we propose that dietary macronutrient composition, an underexplored environmental factor, might play a key role. Variation in macronutrient composition can lead to among-individual differentiation in single behaviours (‘personality’ ) as well as among-individual covariation between behaviours (‘behavioural syndromes’ ). Here, we argue that the nutritional balance during any life stage might affect the development of syndrome structure and the expression of genes with pleiotropic effects that influence development of multiple behaviours, hence genetic syndrome structure. We further suggest that males and females should typically differ in diet-dependent genetic syndrome structure despite a shared genetic basis. We detail how such diet-dependent multivariate gene-environment interactions can have major repercussions for the evolution of behavioural syndromes.

Behavioural responses of feral and domestic guppies (Poecilia reticulata) to predators and their cues

Predation is an important factor during adaptation to novel environments, and the feralisation of introduced domestic species often involves responding appropriately to allopatric predators despite a background of domestication and inbreeding. Twenty years ago, domestic guppies were introduced to a semi-natural environment at Burgers' Zoo in the Netherlands, where they have since been exposed to avian predation. We compared predation-linked behaviours in this feral population and in domestic guppies akin to the original founders. We found that both populations responded to a novel predator and to conspecific alarm cues. However, shoaling, an important anti-predator behaviour, was higher among feral guppies both at baseline and when exposed to the novel predator. We did not observe a linked suite of anti-predator behaviours across shoaling, predator inspection, alarm substance sensitivity and boldness, suggesting that these responses may be decoupled from one another depending on local predation regimes. As we compared two populations, we cannot identify the causal factors determining population differences, however, our results do suggest that shoaling is either a particularly consequential anti-predator adaptation or the most labile of the behaviours we tested. Finally, the behavioural adaptability of domestic guppies may help to explain their success as an invasive species.

Individual consistency in the behaviors of newly-settled reef fish

Flexibility in behavior is advantageous for organisms that transition between stages of a complex life history. However, various constraints can set limits on plasticity, giving rise to the existence of personalities that have associated costs and benefits. Here, we document a field and laboratory experiment that examines the consistency of measures of boldness, activity, and aggressive behavior in the young of a tropical reef fish, Pomacentrus amboinensis (Pomacentridae) immediately following their transition between pelagic larval and benthic juvenile habitats. Newly-settled fish were observed in aquaria and in the field on replicated patches of natural habitat cleared of resident fishes. Seven behavioral traits representing aspects of boldness, activity and aggression were monitored directly and via video camera over short (minutes), medium (hours), and long (3 days) time scales. With the exception of aggression, these behaviors were found to be moderately or highly consistent over all time scales in both laboratory and field settings, implying that these fish show stable personalities within various settings. Our study is the first to examine the temporal constancy of behaviors in both field and laboratory settings in over various time scales at a critically important phase during the life cycle of a reef fish.

Conspicuous female ornamentation and tests of male mate preference in threespine sticklebacks (Gasterosteus aculeatus)

Sexual selection drives the evolution of exaggerated male ornaments in many animal species. Female ornamentation is now acknowledged also to be common but is generally less well understood. One example is the recently documented red female throat coloration in some threespine stickleback (Gasterosteus aculeatus) populations. Although female sticklebacks often exhibit a preference for red male throat coloration, the possibility of sexual selection on female coloration has been little studied. Using sequential and simultaneous mate choice trials, we examined male mate preferences for female throat color, as well as pelvic spine color and standard length, using wild-captured threespine sticklebacks from the Little Campbell River, British Columbia. In a multivariate analysis, we found no evidence for a population-level mate preference in males, suggesting the absence of directional sexual selection on these traits arising from male mate choice. Significant variation was detected among males in their preference functions, but this appeared to arise from differences in their mean responsiveness across mating trials and not from variation in the strength (i.e., slope) of their preference, suggesting the absence of individual-level preferences as well. When presented with conspecific intruder males, male response decreased as intruder red throat coloration increased, suggesting that males can discriminate color and other aspects of phenotype in our experiment and that males may use these traits in intrasexual interactions. The results presented here are the first to explicitly address male preference for female throat color in threespine sticklebacks.

Phenotypic integration between antipredator behavior and camouflage pattern in juvenile sticklebacks

Predation is a strong selective force that promotes the evolution of antipredator behaviors and camouflage in prey animals. However, the independent evolution of single traits cannot explain how observed phenotypic variations of these traits are maintained within populations. We studied genetic and phenotypic correlations between antipredator behaviors (shoaling and risk-taking) and morphology traits (pigmentation and size) in juvenile three-spined sticklebacks by using pedigree-based quantitative genetic analysis to test phenotypic integration (or complex phenotype) as an evolutionary response to predation risk. Individuals with strongly melanized (i.e., camouflaged) phenotype and genotype were less sociable to conspecifics, but bolder during foraging under predation risk. Individuals with faster growing phenotype and genotype were bolder, and those with lager eyes were more fearful. These phenotypic integrations were not confounded with correlated plastic responses to predation risk because the phenotypes were measured in naïve fish born in the laboratory, but originated from a natural population with predation pressure. Consistent selection for particular combinations of traits under predation pressure or pleiotropic genes might influence the maintenance of the genetic (co)variations and polymorphism in melanin color, growth trajectory, and behavior patterns.

Changes in wild red squirrel personality across ontogeny: activity and aggression regress towards the mean

Both juvenile and adult animals display stable behavioural differences (personality), but lifestyles and niches may change as animals mature, raising the question of whether personality changes across ontogeny. Here, we use a wild population of red squirrels to examine changes in activity and aggression from juvenile to yearling life stages. Personality may change at the individual level (individual stability), population level (mean level stability), and relative to other individuals (differential stability). We calculated all three types of stability, as well as the structural stability of the activity–aggression behavioural syndrome. Within individuals, both activity and aggression scores regressed towards the mean. Differential stability was maintained for activity, but not aggression. Structural stability was maintained; however, the activity–aggression correlation increased in squirrels that gained territories later in the season. These results suggest that personality undergoes some changes as animals mature, and that the ontogeny of personality can be linked to environmental changes.

European green lizard (Lacerta viridis) personalities: Linking behavioural types to ecologically relevant traits at different ontogenetic stages

Consistent individual differences within (animal personality) and across (behavioural syndrome) behaviours became well recognized during the past decade. Nevertheless, our knowledge about the evolutionary and developmental mechanisms behind the phenomena is still incomplete. Here, we explored if risk-taking and exploration were consistent and linked to different ecologically relevant traits in wild-caught adult male European green lizards (Lacerta viridis) and in their 2-3 weeks old laboratory-reared offspring. Both adults and juveniles displayed animal personality, consistency being higher in juveniles. We found correlation between risk-taking and exploration (suggestive of a behavioural syndrome) only in adults. Juveniles were more explorative than adults. Large or ectoparasite-free adult males were more explorative than small or parasitized males. Juvenile females tended to be more risk-taking than males. Behaviour of fathers and their offspring did not correlate. We conclude that European green lizards show high behavioural consistency and age is an important determinant of its strength and links to traits likely affecting fitness.

Assessing multivariate constraints to evolution across ten long-term avian studies

Background

In a rapidly changing world, it is of fundamental importance to understand processes constraining or facilitating adaptation through microevolution. As different traits of an organism covary, genetic correlations are expected to affect evolutionary trajectories. However, only limited empirical data are available.

Methodology/Principal Findings

We investigate the extent to which multivariate constraints affect the rate of adaptation, focusing on four morphological traits often shown to harbour large amounts of genetic variance and considered to be subject to limited evolutionary constraints. Our data set includes unique long-term data for seven bird species and a total of 10 populations. We estimate population-specific matrices of genetic correlations and multivariate selection coefficients to predict evolutionary responses to selection. Using Bayesian methods that facilitate the propagation of errors in estimates, we compare (1) the rate of adaptation based on predicted response to selection when including genetic correlations with predictions from models where these genetic correlations were set to zero and (2) the multivariate evolvability in the direction of current selection to the average evolvability in random directions of the phenotypic space. We show that genetic correlations on average decrease the predicted rate of adaptation by 28%. Multivariate evolvability in the direction of current selection was systematically lower than average evolvability in random directions of space. These significant reductions in the rate of adaptation and reduced evolvability were due to a general nonalignment of selection and genetic variance, notably orthogonality of directional selection with the size axis along which most (60%) of the genetic variance is found.

Conclusions

These results suggest that genetic correlations can impose significant constraints on the evolution of avian morphology in wild populations. This could have important impacts on evolutionary dynamics and hence population persistence in the face of rapid environmental change.

Consistency in boldness, activity and exploration at different stages of life

BACKGROUND

Animals show consistent individual behavioural patterns over time and over situations. This phenomenon has been referred to as animal personality or behavioural syndromes. Little is known about consistency of animal personalities over entire life times. We investigated the repeatability of behaviour in common voles (Microtus arvalis) at different life stages, with different time intervals, and in different situations. Animals were tested using four behavioural tests in three experimental groups: 1. before and after maturation over three months, 2. twice as adults during one week, and 3. twice as adult animals over three months, which resembles a substantial part of their entire adult life span of several months.

RESULTS

Different behaviours were correlated within and between tests and a cluster analysis showed three possible behavioural syndrome-axes, which we name boldness, exploration and activity. Activity and exploration behaviour in all tests was highly repeatable in adult animals tested over one week. In animals tested over maturation, exploration behaviour was consistent whereas activity was not. Voles that were tested as adults with a three-month interval showed the opposite pattern with stable activity but unstable exploration behaviour.

CONCLUSIONS

The consistency in behaviour over time suggests that common voles do express stable personality over short time. Over longer periods however, behaviour is more flexible and depending on life stage (i.e. tested before/after maturation or as adults) of the tested individual. Level of boldness or activity does not differ between tested groups and maintenance of variation in behavioural traits can therefore not be explained by expected future assets as reported in other studies.