Behaviour under predation risk - antipredator strategies, behavioural syndromes and sex-specific responses in aquatic prey

Abstract: In many natural ecosystems, predation is well recognized as a strong evolutionary force, and predator-mediated selection has been demonstrated to induce changes in prey morphology, life history and behaviour. In my thesis, I have focused on behavioural responses in aquatic prey under the risk of predation. I have used two different species of prey, the guppy (Poecilia reticulata) from high and low predation communities, and the freshwater isopod Asellus aquaticus that occurs in two distinct ecotypes which encounter contrasting predator faunas. To detect the presence of predators, waterborne predator cues are of great importance for many aquatic prey animals. I found that exposure to predator chemical cues can change male courtship behaviour, and elicit threat-sensitive antipredator responses matching the level of risk posed by the predator in guppies. Furthermore, in the isopod system the sexes exhibited threat-sensitive behaviour with males showing stronger avoidance responses, and cues from different predator types inducing graded antipredator behaviours. Antipredator responses in lab-raised individuals were weaker than in wild-caught ones, potentially indicating a role for learning by prior experience. Recent studies suggest that predation can be an important selective factor shaping animal personality traits. Using a number of specific assays, I measured several different behavioural traits, and in some of my studies these behaviours were analysed using a behavioural syndrome framework. I found that boldness can vary significantly between individuals from high and low predation environments as well as between the sexes. In general, individuals from high predation localities are bolder, and males are more prone to take risks than females. Sex-specific boldness likely mirrors overall differences in life-history strategies between the sexes. Moreover, temperature which is a key environmental factor for many ectotherms had the potential to influence personality traits, but the effect strongly depended on the behavioural measure investigated. In addition, I used Asellus isopods to explore the divergence of phenotypic integration patterns, and behavioural syndromes during the process of colonising a novel habitat. The results show that the phenotypic expression of behavioural traits has changed, and I found evidence for tighter behavioural correlations in the ancestral habitat compared to the novel habitat. The genetic data clearly shows that colonisation has altered the genetic covariance structure of the behavioural traits and populations have differentiated in behavioural syndromes in a very short ecological and evolutionary time frame.