Individual behavioural consistency and plasticity in an urban spider

Exploring behavioral traits over different contexts in four species of Australian funnel-web spiders

Australian funnel-web spiders are arguably the most venomous spiders in the world, with much research focusing on this aspect of their biology. However, other aspects related to their life history, ecology and behaviour have been overlooked. For the first time, we assessed repeatability, namely risk-taking behaviour, aggressiveness and activity in the contexts of predation, conspecific tolerance and exploration of a new territory in four species of Australian funnel-web spiders: two are closely related, Hadronyche valida and H. infensa, and two have overlapping distributions but occupy different habitats, H. cerberea and Atrax robustus. We also compared behaviors between species. At the species level, we found that H. valida showed consistency in risk-taking behavior when exposed to a predator stimulus, aggressiveness against conspecifics, and exploration of a new territory. In contrast, in the other species, only A. robustus showed repeatability in the context of exploration of a new territory. These results suggest that some behavioral traits are likely more flexible than others, and that the repeatability of behaviors may be species-specific in funnel-webs. When we compared species, we found differences in risk-taking behavior and defensiveness. This study provides novel insights to understanding variation in behavioral traits within and between species of funnel-web spiders, suggesting that some behavioral traits are likely context and/or species dependent, as a result of their evolutionary history. These findings provide key insights for understanding the ecological role of behavior and venom deployment in venomous animals, and a greater understanding of behavior in these medically significant and iconic spiders that are of conservation concern.

The effects of urban life on animal immunity: Adaptations and constraints

Land transformation, including urbanization, is a dominant form of anthropogenic change to the global environment at the dawn of the Anthropocene epoch. More and more species are brought into direct contact with humans, being either required to develop broad-scale adaptations to urban environment or filtered out from urbanized areas. While behavioural or physiological adaptations are at the forefront of urban biology research, there is accumulating evidence for divergent pathogen pressure across urbanization gradients, requiring adjustments in host immune function. At the same time, host immunity may be constrained by unfavourable components of an urban environment, such as poor-quality food resources, disturbance, or pollution. Here, I reviewed existing evidence for adaptations and constrains in the immune system of urban animals, focusing on the recent implementation of metabarcoding, genomic, transcriptomic, and epigenomic approaches in urban biology research. I show that spatial variation in pathogen pressure across urban and non-urban landscapes is highly complex and may be context-dependent, but there is solid evidence for pathogen-driven immunostimulation in urban-dwelling animals. I also show that genes coding for molecules directly involved in interactions with pathogens are the prime candidates for immunogenetic adaptations to urban life. Evidence emerging from landscape genomics and transcriptomics show that immune adaptations to urban life may have a polygenic nature, but immune traits may not be among the key biological functions experiencing broad-scale microevolutionary changes in response to urbanization. Finally, I provided recommendations for future research, including i) a better integration of different 'omic' approaches to obtain a more complete picture of immune adaptations to urban life in non-model animal taxa, ii) quantification of fitness landscapes for immune phenotypes and genotypes across urbanization gradient, and iii) much broader taxonomic coverage (including invertebrates) necessary to draw more robust conclusions on how general (or taxa-specific) are immune responses of animals to urbanization.

Sex-specific life-history strategies among immature jumping spiders: Differences in body parameters and behavior

Selection forces often generate sex-specific differences in various traits closely related to fitness. While in adult spiders (Araneae), sexes often differ in coloration, body size, antipredator, or foraging behavior, such sex-related differences are less pronounced among immatures. However, sex-specific life-history strategies may also be adaptive for immatures. Thus, we hypothesized that among spiders, immature individuals show different life-history strategies that are expressed as sex-specific differences in body parameters and behavioral features, and also in their relationships. We used immature individuals of a protandrous jumping spider, Carrhotus xanthogramma, and examined sex-related differences. The results showed that males have higher mass and larger prosoma than females. Males were more active and more risk tolerant than females. Male activity increased with time, and larger males tended to capture the prey faster than small ones, while females showed no such patterns. However, females reacted to the threatening abiotic stimuli more with the increasing number of test sessions. In both males and females, individuals with better body conditions tended to be more risk averse. Spiders showed no sex-specific differences in interindividual behavioral consistency and in intraindividual behavioral variation in the measured behavioral traits. Finally, we also found evidence for behavioral syndromes (i.e., correlation between different behaviors), where in males, only the activity correlated with the risk-taking behavior, but in females, all the measured behavioral traits were involved. The present study demonstrates that C. xanthogramma sexes follow different life-history strategies even before attaining maturity.

Selecting aggressiveness to improve biological control agents efficiency

In agroecosystems, omnivorous predators are recognized as potential biological control agents because of the numerous pest species they prey on. Nonetheless, it could be possible to enhance their efficiency through artificial selection on traits of economical or ecological relevance. Aggressiveness, which defines the readiness of an individual to display agonistic actions toward other individuals, is expected to be related to zoophagy, diet preferences and to a higher attack rate. The study aimed to assess the aggressiveness degree of the damsel bug, Nabis americoferus, and to estimate its heritability. We hypothesized that a high aggressiveness degree can be selected, and that males are more aggressive than females. Using artificial selection, we reared two separate populations, each composed of nine genetically isolated lines characterized by their different aggressiveness degree (aggressive, docile and non-selected). After three generations, we had efficiently selected aggressive behavior. The realized heritability was 0.16 and 0.27 for aggressiveness and docility in the first population. It was 0.25 and 0.23 for the second population. Males were more aggressive than females only for the second population. The potential of these individuals as biological control agents and the ecological consequences of aggressiveness are discussed.

Urban forest invertebrates: how they shape and respond to the urban environment

Invertebrates comprise the most diversified animal group on Earth. Due to their long evolutionary history and small size, invertebrates occupy a remarkable range of ecological niches, and play an important role as “ecosystem engineers” by structuring networks of mutualistic and antagonistic ecological interactions in almost all terrestrial ecosystems. Urban forests provide critical ecosystem services to humans, and, as in other systems, invertebrates are central to structuring and maintaining the functioning of urban forests. Identifying the role of invertebrates in urban forests can help elucidate their importance to practitioners and the public, not only to preserve biodiversity in urban environments, but also to make the public aware of their functional importance in maintaining healthy greenspaces. In this review, we examine the multiple functional roles that invertebrates play in urban forests that contribute to ecosystem service provisioning, including pollination, predation, herbivory, seed and microorganism dispersal and organic matter decomposition, but also those that lead to disservices, primarily from a public health perspective, e.g., transmission of invertebrate-borne diseases. We then identify a number of ecological filters that structure urban forest invertebrate communities, such as changes in habitat structure, increased landscape imperviousness, microclimatic changes and pollution. We also discuss the complexity of ways that forest invertebrates respond to urbanisation, including acclimation, local extinction and evolution. Finally, we present management recommendations to support and conserve viable and diverse urban forest invertebrate populations into the future.

Transmission of nanoplastics from Culex quinquefasciatus to Pardosa pseudoannulata and its impact on predators

Many studies have explored the effects of plastic particles on aquatic organisms. To date, however, few studies have reported on the effects of plastic particles on terrestrial invertebrates. Here, Culex quinquefasciatus (southern house mosquito, prey) and Pardosa pseudoannulata (wolf spider, predator) were used to explore the transmission of nanoplastics (NPs) from aquatic to terrestrial invertebrates and to verify the effects of NPs in prey on predators. Mosquito larvae were exposed to 0, 200, and 1000 NPs mL^-1 polystyrene, respectively, and then fed to spiders when they matured. Results showed that ingestion of NP-exposed mosquitoes affected the growth, development, and behavior of P. pseudoannulata, and the intestinal tissue structure, intestinal flora composition, and related enzymatic activities were also impacted. These results indicate that after spiders ingested NP-exposed mosquitoes, their growth, development, and predation ability were affected. This may prolong time to maturation and decrease the ability of spiders to survive and reproduce in the environment. Thus, plastic particles likely have a wide range of effects on organisms as well as the whole ecosystem.

The Use of Tuning Forks for Studying Behavioural Responses in Orb Web Spiders

Simple Summary

Spiders are common predators found in almost every type of environment, and are used as model organisms in studies ranging from communication and signalling to biochemical studies on their silk. Orb spiders are particularly interesting, as their web provides a cost-effective way to obtain information on their foraging behaviour. However, studies on short-term behaviours including prey capture and escape behaviours are rare and usually take place in artificial settings, such as laboratories. In this study, we tested a simple methodology using tuning forks that can be used consistently and reliably in the field. The two tuning forks are capable of producing attack (440 Hz) and escape (256 Hz) responses from the spiders. We also used a metal wire as a mechanical stimulus for comparison, which as predicted, was less reliable. We demonstrate the usefulness of the methodology by quantitatively investigating how the size of the spider and the size of its web affect predatory and escape response rates in the autumn spider, although no significant effects of either were found. However, our results confirm the ease by which this simple method can be used to conduct behavioural studies of orb spiders in the wild.

Abstract

Spiders and their webs are often used as model organisms to study a wide range of behaviours. However, these behavioural studies are often carried out in the laboratory, and the few field studies usually result in large amounts of video footage and subsequent labour-intensive data analysis. Thus, we aimed to devise a cost- and time-effective method for studying the behaviour of spiders in the field, using the now almost forgotten method of stimulating webs with tuning forks. Our study looked at the viability of using 256 Hz and 440 Hz tuning forks to stimulate, anti-predatory and predatory responses in the orb web spider Metellina segmentata, respectively. To assess the consistency of the behaviours produced, we compared these to direct mechanical stimulation with a metal wire. The results suggest that the tuning forks produce relatively consistent behaviours within and between two years in contrast to the metal wire. We furthermore found no significant effects of spider length or web area on spider reaction times. However, we found significant differences in reaction times between escape and prey capture behaviours, and between tuning forks and the wire. Thus, we demonstrated the potential of tuning forks to rapidly generate quantitative data in a field setting.

Variation in the behaviour of an obligate corallivore is influenced by resource availability

Abstract

Marine environments are subject to increasing disturbance events, and coral reef ecosystems are particularly vulnerable. During periods of environmental change, organisms respond initially through rapid behavioural modifications. Whilst mean population level modifications to behaviour are well documented, how these shifts vary between individuals, and the relative trade-offs that are induced, are unknown. We test whether the frequency and time invested in different behaviours varies both between and within individuals with varying resource availability. To do this, we quantify differences in four key behavioural categories (aggression, exploration, feeding and sociability) at two sites of different resource availability, using an obligate corallivore butterflyfish species (Chaetodon lunulatus). Individuals on a low resource site held larger territories, investing more time in exploration, which was traded off with less time invested on aggression, feeding and sociability. Repeatability measures indicated that behavioural differences between sites could plausibly be driven by both plasticity of behaviour within individuals and habitat patchiness within feeding territories. By combining population-level means, co-correlation of different behaviours and individual-level analyses, we reveal potential mechanisms behind behavioural variation in C. lunulatus due to differences in resource availability.

Significance statement

Using observational methods, we identify differences in the behaviour of an obligate corallivorous butterflyfish (Chaetodon lunulatus) between a high and a low resource site. We use a combination of density surveys, territory mapping and behavioural observation methods in a comparative analysis to relate behaviour directly to the environment in which it occurs. Bringing together insights from game theory and optimal foraging, we also use our results to highlight how understanding the correlations of different behaviours can inform our understanding of the extent to which behaviours are plastic or fixed. Furthermore, by considering how multiple behaviours are correlated, we move away from exploring individual behaviours in isolation and provide an in-depth insight into how differences in behaviour both between individuals and at the population level can affect responses to declining resource availability.

A physiological profile approach to animal temperament: How to understand the functional significance of individual differences in behaviour

Animal behaviour research has experienced a renewed interest in consistent individual differences (i.e. animal personality or temperament). Recent ecological studies have identified environmental conditions that give rise to the development and evolution of temperaments and to fitness-related outcomes of temperament. Additional literature has also described relationships between temperaments and physiological regulation. However, one-to-one relationships between one behavioural trait and one physiological system do not account for co-selection of behavioural and physiological traits, nor the complex signalling among physiological systems. In the current paper, we review the literature on multiple physiological processes associated with temperament, propose temperament-specific physiological profiles, and focus on next steps to understand the functional significance, evolution and maintenance of temperaments. We propose that to understand causes and consequences of temperament we need to characterize integrative physiological profiles associated with different temperaments.

No evidence for innate differences in tadpole behavior between natural, urbanized, and invasive populations

Abstract

Animals are increasingly challenged to respond to novel or rapidly changing habitats due to urbanization and/or displacement outside their native range by humans. Behavioral differences, such as increased boldness (i.e., propensity for risk-taking), are often observed in animals persisting in novel environments; however, in many cases, it is unclear how these differences arise (e.g., through developmental plasticity or evolution) or when they arise (i.e., at what age or developmental stage). In the Guttural Toad (Sclerophrys gutturalis), adult urban toads from both native and invasive ranges are bolder than conspecifics in natural habitats. Here, we reared Guttural Toad tadpoles in a common garden experiment, and tested for innate differences in boldness across their development and between individuals whose parents and lineage came from rural-native, urban-native, and urban-invasive localities (i.e., origin populations). Tadpoles did not differ in their boldness or in how their boldness changed over ontogeny based on their origin populations. In general, tadpoles typically became less bold as they aged, irrespective of origin population. Our findings indicate that differences in boldness in free-living adult Guttural Toads are not innate in the tadpole stage and we discuss three possible mechanisms driving phenotypic divergence in adult boldness for the focus of future research: habitat-dependent developmental effects on tadpole behavior, decoupled evolution between the tadpole and adult stage, and/or behavioral flexibility, learning, or acclimatization during the adult stage.

Significance statement

To determine if animals can persist in urban areas or become invasive outside their native ranges, it is important to understand how they adapt to life in the city. Our study investigates if differences in boldness that have been found in adult Guttural Toads (Sclerophrys gutturalis) represent heritable differences that can also be found in early life stages by rearing tadpoles from eggs in a common garden experiment. We did not find any differences in boldness among tadpoles from rural-native, urban-native, and urban-invasive origin populations. Our findings suggest that differences in boldness are not innate and/or that boldness is a behavioral trait that is decoupled between the tadpole and the adult stage.

Gaps to Address in Ecological Studies of Temperament and Physiology

Ecology is a diverse field with many researchers interested in drivers and consequences of variability within populations. Two aspects of variability that have been addressed are behavioral and physiological. While these have been shown to separately influence ecological outcomes such as survival, reproductive success and fitness, combined they could better predict within-population variability in survival and fitness. Recently there has been a focus on potential fitness outcomes of consistent behavioral traits that are referred to as personality or temperament (e.g. boldness, sociability, exploration, etc.). Given this recent focus, it is an optimal time to identify areas to supplement in this field, particularly in determining the relationship between temperament and physiological traits. To maximize progress, in this perspective paper we propose that the following two areas be addressed: (1) increased diversity of species, and (2) increased number of physiological processes studied, with an eye toward using more representative and relatively consistent measures across studies. We first highlight information that has been gleaned from species that are frequently studied to determine how animal personality relates to physiology and/or survival/fitness. We then shine a spotlight on important taxa that have been understudied and that can contribute meaningful, complementary information to this area of research. And last, we propose a brief array of physiological processes to relate to temperament, and that can significantly impact fitness, and that may be accessible in field studies.

The genetic architecture of behavioral traits in a spider

The existence of consistent individual differences in behavior has been shown in a number of species, and several studies have found observable sex differences in these behaviors, yet their evolutionary implications remain unclear. Understanding the evolutionary dynamics of behavioral traits requires knowledge of their genetic architectures and whether this architecture differs between the sexes. We conducted a quantitative genetic study in a sexually size-dimorphic spider, Larinioides sclopetarius, which exhibits sex differences in adult lifestyles. We observed pedigreed spiders for aggression, activity, exploration, and boldness and used animal models to disentangle genetic and environmental influences on these behaviors. We detected trends toward (i) higher additive genetic variances in aggression, activity, and exploration in males than females, and (ii) difference in variances due to common environment/maternal effects, permanent environment and residual variance in aggression and activity with the first two variances being higher in males for both behaviors. We found no sex differences in the amount of genetic and environmental variance in boldness. The mean heritability estimates of aggression, activity, exploration, and boldness range from 0.039 to 0.222 with no sizeable differences between females and males. We note that the credible intervals of the estimates are large, implying a high degree of uncertainty, which disallow a robust conclusion of sex differences in the quantitative genetic estimates. However, the observed estimates suggest that sex differences in the quantitative genetic architecture of the behaviors cannot be ruled out. Notably, the present study suggests that genetic underpinnings of behaviors may differ between sexes and it thus underscores the importance of taking sex differences into account in quantitative genetic studies.

"Micropersonality" traits and their implications for behavioral and movement ecology research

Many animal personality traits have implicit movement-based definitions and can directly or indirectly influence ecological and evolutionary processes. It has therefore been proposed that animal movement studies could benefit from acknowledging and studying consistent interindividual differences (personality), and, conversely, animal personality studies could adopt a more quantitative representation of movement patterns.Using high-resolution tracking data of three-spined stickleback fish (Gasterosteus aculeatus), we examined the repeatability of four movement parameters commonly used in the analysis of discrete time series movement data (time stationary, step length, turning angle, burst frequency) and four behavioral parameters commonly used in animal personality studies (distance travelled, space use, time in free water, and time near objects).Fish showed repeatable interindividual differences in both movement and behavioral parameters when observed in a simple environment with two, three, or five shelters present. Moreover, individuals that spent less time stationary, took more direct paths, and less commonly burst travelled (movement parameters), were found to travel farther, explored more of the tank, and spent more time in open water (behavioral parameters).Our case study indicates that the two approaches-quantifying movement and behavioral parameters-are broadly equivalent, and we suggest that movement parameters can be viewed as "micropersonality" traits that give rise to broad-scale consistent interindividual differences in behavior. This finding has implications for both personality and movement ecology research areas. For example, the study of movement parameters may provide a robust way to analyze individual personalities in species that are difficult or impossible to study using standardized behavioral assays.

Beyond spider personality: The relationships between behavioral, physiological, and environmental factors

Spiders are useful models for testing different hypotheses and methodologies relating to animal personality and behavioral syndromes because they show a range of behavioral types and unique physiological traits (e.g., silk and venom) that are not observed in many other animals. These characteristics allow for a unique understanding of how physiology, behavioral plasticity, and personality interact across different contexts to affect spider's individual fitness and survival. However, the relative effect of extrinsic factors on physiological traits (silk, venom, and neurohormones) that play an important role in spider survival, and which may impact personality, has received less attention. The goal of this review is to explore how the environment, experience, ontogeny, and physiology interact to affect spider personality types across different contexts. We highlight physiological traits, such as neurohormones, and unique spider biochemical weapons, namely silks and venoms, to explore how the use of these traits might, or might not, be constrained or limited by particular behavioral types. We argue that, to develop a comprehensive understanding of the flexibility and persistence of specific behavioral types in spiders, it is necessary to incorporate these underlying mechanisms into a synthesized whole, alongside other extrinsic and intrinsic factors.

Foraging aggressiveness determines trophic niche in a generalist biological control species

There is a growing evidence that consistent interindividual differences in behavior, that is, behavioral types, can play an important role in key ecological processes such as predator–prey interactions, which in turn can have direct implications on biological control. Behavioral types of generalist predators may affect these interactions through individual differences in predators’ prey preferences and the breadth of predators’ trophic niches. This study examined how the multivariate nature of behavior, namely foraging aggressiveness, activity level, and risk-taking behavior, determines prey selection and trophic niche of the generalist agrobiont spider Philodromus cespitum. In laboratory experiments, we determined the repeatability of these behaviors and the preference between crickets, moths, fruit flies, and collembolans. We found that all three behaviors were moderately to strongly repeatable but there were no correlations between them, thus they did not form a behavioral syndrome. Only foraging aggressiveness influenced the prey selection of philodromid spiders and the more aggressive individuals had wider trophic niches because they incorporated prey that were more difficult to capture in their diet. In addition, more aggressive individuals killed a greater quantity of particular prey types while other prey types were killed at a similar rate by both aggressive and nonaggressive individuals. The differences in philodromids’ foraging aggressiveness, therefore, affected not only the overall prey density but also resulted in different prey community composition. As pest density and composition can both affect crop performance, further research needs to investigate how the interindividual behavioral differences of generalist natural enemies cascade down on the crops.

Body Size, Not Personality, Explains Both Male Mating Success and Sexual Cannibalism in a Widow Spider

Theory suggests that consistent individual variation in behavior relates to fitness, but few studies have empirically examined the role of personalities in mate choice, male-male competition and reproductive success. We observed the Mediterranean black widow, Latrodectus tredecimguttatus, in the individual and mating context, to test how body size measures and two functionally important aggressive behaviors, i.e., male aggression towards rivals and female voracity towards prey, affect mating behaviors, mating success and sexual cannibalism. We specifically selected voracity towards prey in females to test the "aggressive spillover hypothesis", suggesting that more voracious females are more sexually cannibalistic. Both females and males exhibit consistent individual differences in the examined aggressive behaviors. While larger males win contests more often and achieve more copulations, neither male nor female size measures correlate to aggression. Female voracity does not correlate with aggression towards mates and sexual cannibalism, rejecting the "spillover hypothesis". However, occurrence of sexual cannibalism positively relates to longer insertion duration. Furthermore, the smaller the ratio between male and female body length the more likely a female attacked and cannibalized a mate. We show that individual variation in aggression levels plays no direct role in the mating behavior of the Mediterranean black widow. Instead, body size affects male mating success and occurrences of sexual cannibalism in females.

Habitat features and colony characteristics influencing ant personality and its fitness consequences

Several factors can influence individual and group behavioral variation that can have important fitness consequences. In this study, we tested how two habitat types (seminatural meadows and meadows invaded by Solidago plants) and factors like colony and worker size and nest density influence behavioral (activity, meanderness, exploration, aggression, and nest displacement) variation on different levels of the social organization of Myrmica rubra ants and how these might affect the colony productivity. We assumed that the factors within the two habitat types exert different selective pressures on individual and colony behavioral variation that affects colony productivity. Our results showed individual-/colony-specific expression of both mean and residual behavioral variation of the studied behavioral traits. Although habitat type did not have any direct effect, habitat-dependent factors, like colony size and nest density influenced the individual mean and residual variation of several traits. We also found personality at the individual-level and at the colony level. Exploration positively influenced the total- and worker production in both habitats. Worker aggression influenced all the productivity parameters in seminatural meadows, whereas activity had a positive effect on the worker and total production in invaded meadows. Our results suggest that habitat type, through its environmental characteristics, can affect different behavioral traits both at the individual and colony level and that those with the strongest effect on colony productivity primarily shape the personality of individuals. Our results highlight the need for complex environmental manipulations to fully understand the effects shaping behavior and reproduction in colony-living species.

Zebra finches bi-directionally selected for personality differ in repeatability of corticosterone and testosterone

Consistent between-individual differences in behaviour have been documented across the animal kingdom. Such variation between individuals has been shown to be the basis for selection and to act as a pacemaker for evolutionary change. Recently, equivocal evidence suggests that such consistent between-individual variation is also present in hormones. This observation has sparked interest in understanding the mechanisms shaping individual differences, temporal consistency and heritability of hormonal phenotypes and to understand, if and to what extent hormonal mechanisms are involved in mediating consistent variation in behaviour between individuals. Here, we used zebra finches of the fourth generation of bi-directionally selected lines for three independent behaviours: aggression, exploration and fearlessness. We investigated how these behaviours responded to artificial selection and tested their repeatability. We further tested for repeatability of corticosterone and testosterone across and within lines. Moreover, we are presenting the decomposed variance components for within-individual variance (i.e. flexibility) and between-individual variance (i.e. more or less pronounced differences between individuals) and investigate their contribution to repeatability estimates. Both hormones as well as the exploration and fearlessness but not aggressiveness, were repeatable. However, variance components and hence repeatability differed between lines and were often lower than in unselected control animals, mainly because of a reduction in between-individual variance. Our data show that artificial selection (including active selection and genetic drift) can affect the mean and variance of traits. We stress the importance for understanding how variable a trait is both between and within individuals to assess the selective value of a trait.

Are personalities genetically determined? Inferences from subsocial spiders

Background

Recent research has revealed that polymorphic behavioral strategies shape intra-and interspecific interactions and contribute to fitness in many animal species. A better understanding of the proximate mechanisms underlying these behavioral syndromes will enhance our grasp this phenomenon. Spiders in the genus Anelosimus exhibit inter-individual behavioral variation on several axes: individuals have consistent responses to stimuli (e.g. bold vs. shy individuals) and they are subsocial (exhibiting extended maternal care and sibling cooperation) across most of their range, but they sometimes form permanent social groups in northern temperate regions. Here, we seek genetic variants associated with boldness and with social structure in a socially polymorphic population of the spider Anelosimus studiosus. We also develop preliminary genomic resources, including a genome assembly and linkage map, that support this and future genomic research on this group.

Results

Remarkably, we identify a small genomic scaffold (~ 1200 bp) that harbors seven single nucleotide polymorphisms (SNPs) associated with boldness. Moreover, heterozygotes are less common than expected based on Hardy-Weinberg equilibrium, suggesting that either assortative mating or selection against heterozygotes may be occurring in this system. We find no loci significantly associated with social organization. Our draft genome assembly allows us to localize SNPs of interest in this study and to carry out genetic comparisons with other published genomes, although it remains highly fragmented.

Conclusions

By identifying a locus associated with a well-studied animal personality trait, this study opens up avenues for future research to link behavioral studies of animal personality with genotype and fitness.

Collective aggressiveness limits colony persistence in high- but not low-elevation sites at Amazonian social spiders

Identifying the traits that foster group survival in contrasting environments is important for understanding local adaptation in social systems. Here, we evaluate the relationship between the aggressiveness of social spider colonies and their persistence along an elevation gradient using the Amazonian spider, Anelosimus eximius. We found that colonies of A. eximius exhibit repeatable differences in their collective aggressiveness (latency to attack prey stimuli) and that colony aggressiveness is linked with persistence in a site-specific manner. Less aggressive colonies are better able to persist at high-elevation sites, which lack colony-sustaining large-bodied prey, whereas colony aggression was not related to chance of persistence at low-elevation sites. This suggests that low aggressiveness promotes colony survival in high-elevation, prey-poor habitats, perhaps via increased tolerance to resource limitation. These data reveal that the collective phenotypes that relate to colony persistence vary by site, and thus, the path of social evolution in these environments is likely to be affected.

Sex differences in the genetic architecture of aggressiveness in a sexually dimorphic spider

Sex differences in the genetic architecture of behavioral traits can offer critical insight into the processes of sex-specific selection and sexual conflict dynamics. Here, we assess genetic variances and cross-sex genetic correlations of two personality traits, aggression and activity, in a sexually size-dimorphic spider, Nuctenea umbratica. Using a quantitative genetic approach, we show that both traits are heritable. Males have higher heritability estimates for aggressiveness compared to females, whereas the coefficient of additive genetic variation and evolvability did not differ between the sexes. Furthermore, we found sex differences in the coefficient of residual variance in aggressiveness with females exhibiting higher estimates. In contrast, the quantitative genetic estimates for activity suggest no significant differentiation between males and females. We interpret these results with caution as the estimates of additive genetic variances may be inflated by nonadditive genetic effects. The mean cross-sex genetic correlations for aggression and activity were 0.5 and 0.6, respectively. Nonetheless, credible intervals of both estimates were broad, implying high uncertainty for these estimates. Future work using larger sample sizes would be needed to draw firmer conclusions on how sexual selection shapes sex differences in the genetic architecture of behavioral traits.

Behaviour, morphology and microhabitat use: what drives individual niche variation?

Generalist populations are often composed of individuals each specialized on only a subset of the resources exploited by the entire population. However, the traits underlying such niche variation remain underexplored. Classically, ecologists have focused on understanding why populations vary in their degree of intraspecific niche variation, with less attention paid to how individual-level traits lead to intraspecific differences in niches. We investigated how differences in behaviour, morphology and microhabitat affect niche variation between and within individuals in two species of spider Anelosimus studiosus and Theridion murarium. Our results convey that behaviour (i.e. individual aggressiveness) was a key driver of intraspecific trophic variation in both species. More aggressive individuals capture more prey, but particularly more Coleoptera, Hymenoptera and Diptera. These findings suggest that behavioural traits play a critical role in determining individuals' diet and that behaviour can be a powerful force in driving intraspecific niche variation.

Roll with the fear: environment and state dependence of pill bug (Armadillidium vulgare) personalities

Most studies on animal personality evaluate individual mean behaviour to describe individual behavioural strategy, while often neglecting behavioural variability on the within-individual level. However, within-individual behavioural plasticity (variation induced by environment) and within-individual residual variation (regulatory behavioural precision) are recognized as biologically valid components of individual behaviour, but the evolutionary ecology of these components is still less understood. Here, we tested whether behaviour of common pill bugs (Armadillidium vulgare) differs on the among- and within-individual level and whether it is affected by various individual specific state-related traits (sex, size and Wolbachia infection). To this aim, we assayed risk-taking in familiar vs. unfamiliar environments 30 times along 38 days and applied double modelling statistical technique to handle the complex hierarchical structure for both individual-specific trait means and variances. We found that there are significant among-individual differences not only in mean risk-taking behaviour but also in environment- and time-induced behavioural plasticity and residual variation. Wolbachia-infected individuals took less risk than healthy conspecifics; in addition, individuals became more risk-averse with time. Residual variation decreased with time, and individuals expressed higher residual variation in the unfamiliar environment. Further, sensitization was stronger in females and in larger individuals in general. Our results suggest that among-individual variation, behavioural plasticity and residual variation are all (i) biologically relevant components of an individual's behavioural strategy and (ii) responsive to changes in environment or labile state variables. We propose pill bugs as promising models for personality research due to the relative ease of getting repeated behavioural measurements.

The Behavioral Type of a Top Predator Drives the Short-Term Dynamic of Intraguild Predation

Variation in behavior among individual top predators (i.e., the behavioral type) can strongly shape pest suppression in intraguild predation (IGP). However, the effect of a top predator's behavioral type-namely, foraging aggressiveness (number of killed divided by prey time) and prey choosiness (preference degree for certain prey type)-on the dynamic of IGP may interact with the relative abundances of top predator, mesopredator, and pest. We investigated the influence of the top predator's behavioral type on the dynamic of IGP in a three-species system with a top predator spider, a mesopredator spider, and a psyllid pest using a simulation model. The model parameters were estimated from laboratory experiments and field observations. The top predator's behavioral type altered the food-web dynamics in a context-dependent manner. The system with an aggressive/nonchoosy top predator, without prey preferences between pest and mesopredator, suppressed the pest more when the top predator to mesopredator abundance ratio was high. In contrast, the system with a timid/choosy top predator that preferred the pest to the mesopredator was more effective when the ratio was low. Our results show that the behavioral types and abundances of interacting species need to be considered together when studying food-web dynamics, because they evidently interact. To improve biocontrol efficiency of predators, research on the alteration of their behavioral types is needed.

Producers and scroungers: feeding-type composition changes with group size in a socially foraging spider

In groups of socially foraging animals, feeding behaviour may change with group size in response to varying cost-benefit trade-offs. Numerous studies have described group-size effects on group-average feeding behaviour, particularly emphasizing an increase in scrounging incidence for larger groups, where individuals (scroungers) feed from the food sources others (producers) discovered. However, individual variation in feeding behaviour remains unconsidered in the vast majority of these studies even though theoretical models predict individuals to specialize in feeding tactic and anticipate higher scrounger-type frequencies in larger groups. We combined group-level and individual-level analyses of group-size effects on social foraging in the subsocial spider Australomisidia ergandros Lending novel experimental support to model predictions, we found that individuals specialize in feeding tactic and that higher scrounging and lower producing incidence in larger groups were mediated through shifts in the ratio of feeding types. Further, feeding-type specialization was not explained by innate individual differences in hunting ability as all feeding types were equally efficient in prey capture when foraging alone. Context adaptivity of feeding behaviour might allow this subsocial species to succeed under varying socioecological conditions.

Effects of parenting quality on adolescents' personality resemblance to their parents. The TRAILS study

This study considers the development of resemblance between 741 adolescents and their biological parents, across six NEO-PI-R personality traits known to be important in psychological problems: anger-hostility, impulsiveness, vulnerability, assertiveness, excitement-seeking, and self-discipline. We modelled the association between perceived parental warmth and rejection at age eleven and personality resemblance to parents at about age sixteen. Parenting experienced during early adolescence was related to the degree and direction in which adolescents resembled their parents five years later in life. Rejection, especially from fathers, significantly predicted a smaller resemblance to both the parents. Girls were more strongly affected by parental quality than boys, and there was some indication that adolescents responded in opposite ways to parenting from mothers and fathers. This study is a first step in uncovering the complex interplay between parenting, gender, and the current generation's ability to develop personality traits independent from the previous generation.