Browsing by Subject "quantitative genetic variance"

Behaviour is a key component in ecological interactions and studying its role in adaptation is central in our understanding of natural selection and phenotypic variation in the wild. Predation is an important driver shaping animal behaviour in the wild, since predators have been shown to select against particular behavioural phenotypes. However, it is not easy to demonstrate that specific behaviours are adaptive to certain levels of predation, since behaviours are often correlated with each other forming multivariate phenotypes and display notable phenotypic plasticity. I studied how predation shapes genetically determined behaviour of the nine-spined stickleback (Pungitius pungitius) through variation in historical predation pressures and by inducing phenotypic plasticity. This was achieved through rearing 65 full-sib families of nine-spined sticklebacks derived from four coastal marine (predator-sympatric) and four pond (predator-naïve) populations in a common garden experiment and quantifying their behaviour in the laboratory in the presence and absence of natural predators. Since the fish used were F1-generation offspring from artificial crosses, I was also able to estimate the heritability and genetic correlations of the studied behaviours. Pond sticklebacks tended to be more explorative and took more risks during foraging than marine sticklebacks regardless of predation risk. In all fish, predator presence decreased the propensity to take risks during foraging, but not exploration tendency. Since the fish were reared in a common garden setting, there is a genetic basis for these population differences. Both behaviours were heritable in all populations. In this study, I observed genetically based and heritable behavioural differences between pond and marine stickleback populations. Despite showing similar levels of behavioural plasticity as marine sticklebacks, pond sticklebacks were still inappropriately active in the presence of predators and would have a low survival probability in a predator-sympatric environment. In risk-taking during foraging, the behavioural trend caused by acute predation risk was directionally the same as that caused by evolutionary history of predation risk, implying that the behavioural differentiation between marine and pond populations in this behaviour is due to predation. These results provide evidence of local adaptation in behaviour to differing levels of predation in these populations, and that this adaptation comes about as differences in the overall level of behaviour rather than in phenotypic plasticity.