Evolutionary ecology of animal personality

Individual organisms continuously react to their environment in order to maximize their fitness, but interestingly, individuals often differ in their reaction towards the same stimuli. This variation is often not just noise around an optimal strategy, and reactions to different stimuli are frequently structured in ?behavioural syndromes?, comparable to how humans differ in personality. For instance, individuals that are aggressive usually also take more risks in exploring novel environments and predators. While positive phenotypic and genetic correlations between aggressiveness and risk-taking have often been reported, population comparisons in three-spined stickleback now show that the association between these traits differs between populations, with the ?aggressiveness-boldness? syndrome only existing in populations with high predation pressure. These findings illustrate that environmental factors affect phenotypic correlations between components of ?animal personality?. This project aims to elucidate the proximate and ultimate factors shaping behavioural syndromes under different conditions. Using the aggressiveness-boldness syndrome in three-spined stickleback as a highly suitable model system, I will evaluate why the syndrome exist in predator-sympatric but not in predator-naïve populations. Using an artifical breeding program where experience of offspring with both predators and conspecifics is manipulated, sources of (co)variation in aggressiveness and risk-taking behaviour will be measured for both predator-sympatric and predator-naïve populations. I will further explore whether phenotypic correlations emerge from self-organised processes (where interactions between lower levels result in complex patterns at higher levels). Lastly, I plan to assess whether the syndrome is favoured by natural selection in predator-sympatric populations. To do so, semi-wild populations will be established where the presence/absence of predators manipulated and where lifetime fitness is measured as a function of aggressiveness, risk-taking and their interaction. The combination of proximate and ultimate approaches will allow an informed evaluation of how behavioural syndromes evolve in different environments. Keywords: behavioural syndromes; natural selection; phenotypic plasticity; quantitative genetics; predator-prey interactions