The great tit HapMap project: a continental‐scale analysis of genomic variation in a songbird

A major aim of evolutionary biology is to understand why patterns of genomic diversity vary within taxa and space. Large-scale genomic studies of widespread species are useful for studying how environment and demography shape patterns of genomic divergence. Here, we describe one of the most geographically comprehensive surveys of genomic variation in a wild vertebrate to date; the great tit (Parus major) HapMap project. We screened ca 500,000 SNP markers across 647 individuals from 29 populations, spanning ~30 degrees of latitude and 40 degrees of longitude – almost the entire geographical range of the European subspecies. Genome-wide variation was consistent with a recent colonisation across Europe from a South-East European refugium, with bottlenecks and reduced genetic diversity in island populations. Differentiation across the genome was highly heterogeneous, with clear ‘islands of differentiation’, even among populations with very low levels of genome-wide differentiation. Low local recombination rates were a strong predictor of high local genomic differentiation (FST), especially in island and peripheral mainland populations, suggesting that the interplay between genetic drift and recombination causes highly heterogeneous differentiation landscapes. We also detected genomic outlier regions that were confined to one or more peripheral great tit populations, probably as a result of recent directional selection at the species' range edges. Haplotype-based measures of selection were related to recombination rate, albeit less strongly, and highlighted population-specific sweeps that likely resulted from positive selection. Our study highlights how comprehensive screens of genomic variation in wild organisms can provide unique insights into spatio-temporal evolutionary dynamics

Behavioural reaction norms: Animal personality meets individual plasticity

Recent studies in the field of behavioural ecology have revealed intriguing variation in behaviour within single populations. Increasing evidence suggests that individual animals differ in their average level of behaviour displayed across a range of contexts (animal 'personality'), and in their responsiveness to environmental variation (plasticity), and that these phenomena can be considered complementary aspects of the individual phenotype. How should this complex variation be studied? Here, we outline how central ideas in behavioural ecology and quantitative genetics can be combined within a single framework based on the concept of 'behavioural reaction norms'. This integrative approach facilitates analysis of phenomena usually studied separately in terms of personality and plasticity, thereby enhancing understanding of their adaptive nature

Immediate and carry-over effects of perceived predation risk on communication behavior in wild birds

Predation induces strong selection on phenotypic traits, affecting prey via consumptive and nonconsumptive effects. Communication is important for territorial behavior, but can increase susceptibility to predators. Therefore, predation risk should influence prey communication patterns, territoriality, and fitness. We evaluated how this trade-off is resolved via 2 manipulations of perceived predation risk using audio playback in wild great tits (Parus major). In the first experiment, we examined the immediate response of individuals to playback; the second experiment, replicated across 2 years, examined both immediate and carry-over effects (over days) of playback broadcast for a 5-month period (March–July) in 12 nest box populations. Birds exposed to predator sounds showed decreased singing and increased alarming compared to controls, both immediately and on days without play back exposure (carry-over effects). Perceived predation risk did not affect how birds responded to simulated territory intrusions. In combination, these studies’ findings imply that individuals perceive predator vocalizations as “risky” up to days after exposure to predator cues, and adjust their behavior to minimize this risk. However, the lack of effects on territorial aggression implies that individuals are able to weigh the costs of predation against the benefits of each type of vocal behavior. Acknowledging that context changes the relative costs and benefits of antipredator behavior has important consequences for understanding predator–prey dynamics

Behavioural syndromes differ predictably between 12 populations of three-spined stickleback

1. Animals often differ in suites of correlated behaviours, comparable with how humans differ in personality. Constraints on the architecture of behaviour have been invoked to explain why such 'behavioural syndromes' exist. From an adaptationist viewpoint, however, behavioural syndromes should evolve only in those populations where natural selection has favoured such trait covariance, and they should therefore exist only in particular types of population. 2. A comparative approach was used to examine this prediction of the adaptive hypothesis. We measured behavioural correlations in 12 different populations of three-spined stickleback (Gasterosteus aculeatus) and assessed whether they indeed varied consistently according to the selective environment, where population was unit of analysis. 3. For a sample of fry from each population, we measured five different behaviours within the categories of (i) aggression (towards conspecifics); (ii) general activity; and (iii) exploration-avoidance (of novel foods, novel environments and altered environments). 4. We show that behavioural syndromes are not always the same in different types of stickleback population: the often-documented syndrome between aggressiveness, activity and exploratory behaviour existed only in large ponds where piscivorous predators were present. In small ponds where predators were absent, these behaviours were not (or only weakly) associated. 5. Our findings imply that population variation in behavioural syndromes does not result from stochastic evolutionary processes, but may result instead from adaptive evolution of behaviour favouring what should prove to be optimal trait combinations

Data from: Does perceived predation risk affect patterns of extra-pair paternity? A field experiment in a passerine bird

1. Non-consumptive predator effects have been shown to influence a wide range of behavioural, life history, and morphological traits. Extra-pair reproduction is widespread among socially monogamous birds and may incur predation costs. Consequently, altered rates of extra-pair reproduction are expected in circumstances characterized by increased adult perceived predation risk. 2. Additionally, extra-pair reproduction is expected to be most affected for birds with phenotypes that generally increase predation risk (such as more active individuals). 3. In two consecutive years, perceived predation risk was manipulated for great tits, Parus major breeding in 12 nest-box plots by broadcasting sounds of their main predator (European sparrowhawk Accipiter nisus; 6 plots). As a control treatment, sounds of a sympatric, avian non-predator species were broadcasted (Eurasian blackbird, Turdus merula; 6 plots). 4. Levels of extra-pair paternity did not differ between plots with different predation-risk treatments. Males that moved more in a novel environment (more active or ‘faster exploring’) tended to have offspring with fewer partners, but this effect did not vary with predation-risk treatment. 5. From an adaptive viewpoint, predation costs associated with extra-pair reproduction may be small and may not outweigh the benefits of extra-pair behaviour. Research on a broader range of taxa with different mating strategies is now needed to confirm the generality of our findings