Genetics and analysis of quantitative traits

I. the origin of species by means of natural selection

Temperament describes the idea that individual behavioural differences are repeatable over time and across situations. This common phenomenon covers numerous traits, such as aggressiveness, avoidance of novelty, willingness to take risks, exploration, and sociality. The study of temperament is central to animal psychology, behavioural genetics, pharmacology, and animal husbandry, but relatively few studies have examined the ecology and evolution of temperament traits. This situation is surprising, given that temperament is likely to exert an important influence on many aspects of animal ecology and evolution, and that individual variation in temperament appears to be pervasive amongst animal species. Possible explanations for this neglect of temperament include a perceived irrelevance, an insufficient understanding of the link between temperament traits and fitness, and a lack of coherence in terminology with similar traits often given different names, or different traits given the same name. We propose that temperament can and should be studied within an evolutionary ecology framework and provide a terminology that could be used as a working tool for ecological studies of temperament. Our terminology includes five major temperament trait categories: shyness-boldness, exploration-avoidance, activity, sociability and aggressiveness. This terminology does not make inferences regarding underlying dispositions or psychological processes, which may have restrained ecologists and evolutionary biologists from working on these traits. We present extensive literature reviews that demonstrate that temperament traits are heritable, and linked to fitness and to several other traits of importance to ecology and evolution. Furthermore, we describe ecologically relevant measurement methods and point to several ecological and evolutionary topics that would benefit from considering temperament, such as phenotypic plasticity, conservation biology, population sampling, and invasion biology.

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Integrating animal temperament within ecology and evolution.

Repeatability (more precisely the common measure of repeatability, the intra-class correlation coefficient, ICC) is an important index for quantifying the accuracy of measurements and the constancy of phenotypes. It is the proportion of phenotypic variation that can be attributed to between-subject (or between-group) variation. As a consequence, the non-repeatable fraction of phenotypic variation is the sum of measurement error and phenotypic flexibility. There are several ways to estimate repeatability for Gaussian data, but there are no formal agreements on how repeatability should be calculated for non-Gaussian data (e.g. binary, proportion and count data). In addition to point estimates, appropriate uncertainty estimates (standard errors and confidence intervals) and statistical significance for repeatability estimates are required regardless of the types of data. We review the methods for calculating repeatability and the associated statistics for Gaussian and non-Gaussian data. For Gaussian data, we present three common approaches for estimating repeatability: correlation-based, analysis of variance (ANOVA)-based and linear mixed-effects model (LMM)-based methods, while for non-Gaussian data, we focus on generalised linear mixed-effects models (GLMM) that allow the estimation of repeatability on the original and on the underlying latent scale. We also address a number of methods for calculating standard errors, confidence intervals and statistical significance; the most accurate and recommended methods are parametric bootstrapping, randomisation tests and Bayesian approaches. We advocate the use of LMM- and GLMM-based approaches mainly because of the ease with which confounding variables can be controlled for. Furthermore, we compare two types of repeatability (ordinary repeatability and extrapolated repeatability) in relation to narrow-sense heritability. This review serves as a collection of guidelines and recommendations for biologists to calculate repeatability and heritability from both Gaussian and non-Gaussian data.

Repeatability for Gaussian and non-Gaussian data: a practical guide for biologists.

The repeatability of behaviour: a meta-analysis.

We argue that animal temperament is an important concept for wildlife conservation
science and review causes and consequences of evolutionary changes in temperament traits that may occur in captive-breeding programmes. An evolutionary perspective is valid because temperament traits are heritable, linked to fitness and potentially subject to intense selection in captivity. Natural, sexual and artificial selection can cause permanent shifts in temperament, reducing the diversity of temperament traits, diversity that may be critical to reintroduction success. Breeding programmes that ignore temperament risk leading the captive population towards domestication. Furthermore, shifts in temperament may
involve alterations in linked morphological and physiological traits, and selection
may even change functional relationships between traits. Captive-breeding programmes
can reduce changes in temperaments by closely monitoring temperament traits, equalizing reproductive success between temperament morphs and using environmental enrichment to reduce captive stress. Under certain circumstances, knowledge about temperament may also provide a useful tool to optimize captive reproduction and to increase reintroduction success. Outside reintroduction programmes, temperament can mediate responses to human contact, hunting,
exploitation, habitat fragmentation and disease transmission. Consideration of
temperaments could strengthen both captive and wild conservation efforts.

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Wildlife conservation and animal temperament: causes and consequences of evolutionary change for captive, reintroduced, and wild populations

Home-range relocation occurs during natal and breeding dispersal, ontogenetic habitat shifts, and the maintenance of resourceor density-dependent patterns of distribution. Relocating animals are expected to change their behavior to compensate for limited familiarity with the new home range and with neighboring conspecifics; such changes may indicate some of the costs of relocation. Little is known, however, about the magnitude and duration of the changes or about the types of behavior affected. We investigated the short-term (2 day) behavioral changes associated with relocation in the highly territorial longfin damselfish, Stegastes diencaeus. We compared the behavior of newcomers settling into experimentally created vacancies in an established neighborhood with that of the original residents of the same territories. The greatest difference was an increase in the rate of agonistic interactions. Newcomers also used smaller territories, moved more, and fed less. Neighboring damselfishes were less aggressive toward neighbors that expanded into vacant territories than toward ‘‘strangers’’ that relocated from elsewhere. The behavior of newcomers approached that of original residents within 2 days but territory size did not. These observations suggest that relocating a territory increases energy expenditure and decreases energy intake. Such costs could explain the philopatry of reef fish when alternative locations are of uncertain quality or are only slightly better. Nevertheless, they are unlikely to outweigh the long-term benefits of obtaining a superior territory—especially for individuals from adjacent territories. Key words: aggression, dear‐enemy, dispersal, foraging, Pomacentridae, postsettlement movement. [Behav Ecol]

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Peter T. McDougall

Papers

Integrating animal temperament within ecology and evolution.

Wildlife conservation and animal temperament: causes and consequences of evolutionary change for captive, reintroduced, and wild populations

Short-term behavioral consequences of territory relocation in a Caribbean damselfish, Stegastes diencaeus