Urbanisation and sex affect the consistency of butterfly personality across metamorphosis

How to measure exploration: A combined estimation method

The personality axis 'exploration-avoidance' is often measured using an open field test (OFT) from which measurements such as mobility level (e.g. distance travelled) and space use (e.g. area covered) in an unknown environment are extracted. Recently developed tracking software surprisingly includes only a measure of mobility level in their output summary. Consequently, recent articles using these software programs started to ignore a measure of space use in their determination of exploration. In this short communication, we show briefly why it is important to not overlook a measure of space use, provide an easy way to calculate such a measure, with adjustable resolution, from the available position data provided by the software and a method to determine a proxy for exploration.

A meta-analysis of sex differences in animal personality: no evidence for the greater male variability hypothesis

The notion that men are more variable than women has become embedded into scientific thinking. For mental traits like personality, greater male variability has been partly attributed to biology, underpinned by claims that there is generally greater variation among males than females in non-human animals due to stronger sexual selection on males. However, evidence for greater male variability is limited to morphological traits, and there is little information regarding sex differences in personality-like behaviours for non-human animals. Here, we meta-analysed sex differences in means and variances for over 2100 effects (204 studies) from 220 species (covering five broad taxonomic groups) across five personality traits: boldness, aggression, activity, sociality and exploration. We also tested if sexual size dimorphism, a proxy for sex-specific sexual selection, explains variation in the magnitude of sex differences in personality. We found no significant differences in personality between the sexes. In addition, sexual size dimorphism did not explain variation in the magnitude of the observed sex differences in the mean or variance in personality for any taxonomic group. In sum, we find no evidence for widespread sex differences in variability in non-human animal personality.

Are There Personality Differences between Rural vs. Urban-Living Individuals of a Specialist Ground Beetle, Carabus convexus?

Simple Summary

Urbanization causes substantial changes in environmental and habitat conditions. These, as well as more frequent disturbance events accompanying urbanization constitute selective forces acting on various reactions of urban-associated species, including behavior. In this study, rural and urban individuals of a forest specialist ground beetle, Carabus convexus were tested for their exploratory and risk-taking behavior. Beetles responded consistently in the different contexts, and also over time, demonstrating that they had personalities. Carabus convexus is the second ground beetle species in which the existence of personality was demonstrated. By agglomerative cluster analysis, we identified two groups of behavioral traits: the exploratory and the risk-taking dimensions of personality. Urban females were significantly more exploratory than urban males which can be an adaptation to find high quality food needed to mature eggs, as well as to find favorable microsites for oviposition. Moreover, urban females and males showed higher level of risk-taking behavior than rural females. Urban beetles with higher risk-taking behavior may be better able to cope with new conditions created by frequent urbanization-driven disturbance events.

Abstract

The world-wide, rapid urbanization is leading to substantial changes in environmental and habitat conditions. These changes, as well as disturbances accompanying urbanization have considerable effects at various levels of the biological organization on wildlife. Understanding behavioral responses to such changes is essential for identifying which organisms may successfully adapt to the altered conditions. In this study, individuals of a forest specialist ground beetle, Carabus convexus, from rural and urban forest patches were tested for their exploratory and risk-taking behavior. Beetles responded consistently in the different contexts; furthermore, by behaving consistently over time, demonstrated that they had personalities. Agglomerative cluster analysis identified two groups of behavioral traits: the exploratory and the risk-taking dimension of personality. Urban females were significantly more exploratory than urban males which can be an adaptation to find high quality food needed to mature eggs in urban habitats, as well as to select favorable microsites for oviposition. Moreover, urban females and males showed more risk-taking behavior than rural females. Urban beetles with more risk-taking behavior may be better able to cope with frequent urbanization-driven disturbance events.

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.

Selective disappearance does not underlie age-related changes in trait repeatability in red squirrels

Understanding the causes and consequences of repeatable among-individual differences in behavior (i.e., animal personality) is a major area of research in behavioral and evolutionary ecology. Recently, attention has turned to understanding the processes behind changes in repeatability through ontogeny because of their implications for populations. We evaluated the relative importance of selective disappearance (i.e., differential mortality), an among-individual mechanism, in generating age-related changes in the repeatability of aggression and activity in juvenile North American red squirrels (Tamiasciurus hudsonicus). We observed age-related decreases in the repeatability of aggression across ages, arising from lower among-individual variance. Although we found evidence for directional selection on aggressiveness, it was insufficient to erode among-individual variance. Thus, ontogenetic decreases in the repeatability of aggression do not appear to be due to selective disappearance. In contrast, the repeatability of activity was higher across ages due to higher among-individual variance in activity, but there was no support for selective disappearance based on activity. Taken together, our results suggest that age-related changes in trait repeatability in red squirrels are not the result of selective disappearance and instead may be the result of within-individual developmental processes, such as individual differences in developmental trajectories.

Growing in the city: Urban evolutionary ecology of avian growth rates

INTRODUCTION

Rapid environmental change driven by urbanization offers a unique insight into the adaptive potential of urban-dwelling organisms. Urban-driven phenotypic differentiation is increasingly often demonstrated, but the impact of urbanization (here modelled as the percentage of impervious surface (ISA) around each nestbox) on offspring developmental rates and subsequent survival remains poorly understood. Furthermore, the role of selection on urban-driven phenotypic divergence was rarely investigated to date.

METHODS AND RESULTS

Data on nestling development and body mass were analysed in a gradient of urbanization set in Warsaw, Poland, in two passerine species: great tits (Parus major) and blue tits (Cyanistes caeruleus). Increasing levels of impervious surface area (ISA) delayed the age of fastest growth in blue tits. Nestling body mass was also negatively affected by increasing ISA 5 and 10 days after hatching in great tits, and 10 and 15 days in blue tits, respectively. High levels of ISA also increased nestling mortality 5 and 10 days after hatching in both species. An analysis of selection differentials performed for two levels of urbanization (low and high ISA) revealed a positive association between mass at day 2 and survival at fledging.

DISCUSSION

This study confirms the considerable negative impact of imperviousness-a proxy for urbanization level-on offspring development, body mass and survival, and highlights increased selection on avian mass at hatching in a high ISA environment.

Adaptive Evolution in Cities: Progress and Misconceptions

Current narratives suggest that urban adaptation - the adaptive evolution of organisms to cities - is pervasive across taxa and cities. However, in reviewing hundreds of studies, we find only six comprehensive examples of species adaptively evolving to urbanization. We discuss the utility and shortcomings of methods for studying urban adaptation. We then review diverse systems offering preliminary evidence for urban adaptation and outline a research program for advancing its study. Urban environments constitute diverse, interacting selective agents that test the limits of adaptation. Understanding urban adaptation therefore offers unique opportunities for addressing fundamental questions in evolutionary biology and for better conserving biodiversity in cities. However, capitalizing on these opportunities requires appropriate research methods and dissemination of accurate narratives.

High human disturbance decreases individual variability in skink escape behavior

Animals living around people may modify their antipredator behavior as a function of proximity to humans, and this response has profound implications for whether or not a population can coexist with humans. We asked whether inland blue-tailed skinks Emoia impar modified their individual antipredator behavior as a function of differential exposure to humans. We conducted multiple consecutive flushes and recorded 2 measures of antipredator response: flight initiation distance (FID), the distance from a threatening stimulus at which an individual flees, and distance fled, the distance an individual fled after a flush. We used a multiple model comparison approach to quantify variation in individual escape behavior across multiple approaches and to test for differences in between-individual variation among populations. We found that individuals tolerated closer approach and fled shorter distances at locations with relatively less human disturbance than at locations with medium and high human disturbance, respectively. In addition, skinks living at high human disturbance sites had less variable FIDs than at low human disturbance sites. Two theories may explain these results. Selection against less favorable phenotypes has reduced behavioral variation in urban habitats and behavioral plasticity allows individuals to flexibly adjust their behavioral patterns in response to human disturbance. These results highlight the importance of studying variation within populations, at the individual level, which may better elucidate the impact that human disturbance has on the behavioral composition of populations.