Sex-specific behavioral flexibility in rapid adaptation to a new environment

Behavioral adaptations are considered an important factor of population success in colonizing novel environments. Individuals can be selected for specific behavioral traits during transport, introduction and especially establishment phase of the invasion process. Aside from population level average of behavioral traits, both among- and within individual variability can contribute to achieving behavioral optima for efficiently acquiring resources in new habitats. Here, we study activity/exploration behavioral traits and boldness in a novel insular population of Italian wall lizard (Podarcis siculus) with a known colonizing history and propagule pressure. We apply Bayesian mixed-effects models and variance partitioning to compare the activity/exploration behavioral traits and boldness between ancestral population from Pod Kopište island and novel population from Pod Mrčaru island.

We found no difference in average levels of activity/exploration behavioral traits (distance moved and angular velocity) or boldness between populations or sexes. Among-individual variance in both behaviors was preserved in novel population, despite small propagule size of ten individuals. Females from ancestral Pod Kopište had substantially lower within-individual variability of distance moved than males. However, females within-individual variability for this trait increased in the novel Pod Mrčaru population, while males remained the same. Females on Pod Mrčaru population also exhibited strong increase in within-individual variability in angular velocity, even surpassing the values denoted for males in that population. In contrast, within-individual variance in boldness did not differ across population by sex groups.

Our results show that among-individual behavioral variation can be preserved even in populations founded by small propagule. Our study also demonstrates sexual dimorphism in the within-individual variability of activity/exploration behavioral traits, both within the populations and in the direction and intensity of change in a new environment. Collectively, this study highlights the importance of studying behavioral flexibility in addition to average population or individual behavioral traits and emphasizes the role of females' activity/exploration in adaptation to new environments.