Personality variation in the butterfly Pararge aegeria: the role of landscape, age and contest ability by Aurélien Kaiser

Urbanization and agriculture are strongly modifying natural ecosystems and these land use changes are now considered as major drivers of biodiversity change. Yet, some species appear to be able to deal with human-created environments. However, because these settings show altered biotic and abiotic conditions, we may expect phenotypic adjustments as a response to a life in urban and agricultural areas.

In this thesis, I studied personality differences between woodland, agricultural and urban populations of the speckled wood butterfly (Pararge aegeria), a former forest specialist that successfully colonised anthropogenic habitats. Using behavioural tests that quantify variation in boldness, activity and exploration, I show that butterflies from different landscapes of origin differed regarding mean levels of boldness and syndrome structure (i.e. the correlation between personality traits). As these experiments involved laboratory-reared individuals, results suggest a genetic basis to the observed differences. The conducted experiments also shed light on environmental conditions that affect personality traits through phenotypic plasticity, including age and intraspecific interactions (i.e. male-male fights). Additionally, I show that developmental conditions affect the repeatability of behavioural traits. Using different experimental approaches, I also tested the ecological relevance of personality traits in the speckled wood butterfly. While boldness does not correlate with aspects of spatial use, more active males were more likely to win territorial fights, which may give them a fitness advantage.

Together, these results provide valuable insights into the field of invertebrate personality – a group that has been rather overlooked in the context of animal personality – and they contribute to understanding the response of species to human activities.