Investigating the syndrome: Ecological and evolutionary implications of personality variation

Animal personality refers to the ecological phenomenon whereby individuals within populations consistently vary in a range of behaviours across time and context (i.e. a personality or behavioural type), and these behaviours can also become correlated (i.e. a behavioural syndrome). Such consistent individual differences in behaviour are evolutionarily intriguing because they suggest limited behavioural plasticity, a departure from traditional optimality theory, and may provide an explanation for seemingly maladaptive behaviour in the wild. Thus, understanding how and why personality varies between individuals and identifying the mechanisms underpinning this variation represent an important research area in behavioural and evolutionary ecology. Animal personality may also provide insight into important ecological issues, such as biological invasions. Accordingly, my thesis explores the ecological and evolutionary implications of personality variation using a repeatedly successful invasive species as a model, the delicate skink, Lampropholis delicata. A common theme throughout this thesis is that I investigate personality variation within broader ecological contexts, and attempt to provide insight into the role animal personality may play in the delicate skink’s successful invasion history.
   In the first part of the thesis, I examine the presence of personality variation within the delicate skink and the consequences of this variation for ecological sampling (Chapter 2). I find significant repeatable behavioural variation in the delicate skink and the presence of an activity-exploration-social syndrome, but no evidence of personality-biased sampling. These results suggest that sampling bias due to animal personality may not be an inevitable outcome, but instead capture bias may only be associated with passive trapping methods that require individuals to respond to the novelty of the trap itself.
   I then document how personality varies between the sexes (Chapter 3) and among geographically distinct populations (Chapter 4) in order to assess the selective processes that could be underlying behavioural trait correlations. I find that personality does not differ greatly between males and females, suggesting that certain personality traits may be evolutionarily constrained and not easily modified by sex-based selection. In contrast, I did find a high degree of personality variation among four geographically distinct native-range source populations, indicating that the frequency of personalities within a population is adapted to local environmental conditions. However, the occurrence of the same behavioural syndromes in each population also suggests a lack of evolutionary independence and support for the constraint hypothesis.
   In Chapter 5, I address whether thermal physiology is a potential mechanism underpinning personality variation in the delicate skink. Indeed, I find evidence for a thermal-behavioural syndrome, whereby an individual’s placement along a thermal physiological axis corresponded with their placement along a personality axis. This thermal-behavioural syndrome also mediated an individual’s habitat selection in an artificial environment, suggesting a link between animal personality, physiology and ecological niche specialisation.
   Finally, I aimed to determine whether personality was linked to dispersal, an important ecological process tied to invasions (Chapter 6). Skinks that were more aggressive, dispersed further and faster than their less aggressive counterparts suggesting the presence of aggression-dependent dispersal. Alternatively, the competitive environment may have influenced an individual’s decision to disperse regardless of their personality. This study indicates that aggression is an important mechanism mediating the propensity to disperse in the delicate skink.
   Together, the results of my thesis provide insights into the adaptive and evolutionary potential of animal personalities and how these consistent individual differences in behaviour impact key ecological issues, including the processes that drive species invasions.