Behavioural variation in the invasive cellar spider Pholcus manueli (Araneae: Pholcidae).

Behaviours such as boldness and exploration are highly plastic and as such, we expect differences between populations, especially for invasive species. In particular, populations at the leading edge of an invasion front may display differences in these behaviours relative to long established core populations as they are often key to their dispersal and invasion success. Likewise, in species with sexual dimorphism, the importance of these behaviours to invasion success may differ for males and females. Here we report on an invasive cellar spider, Pholcus manueli (Araneae: Pholcidae), that is expanding westward across the United States. We investigated whether boldness in response to simulated predator cues (physical and airborne disturbances) and exploration of a novel environment varied across P. manueli's invasive range and between males and females. We found significant differences in the reaction to the simulated predator cues, but not in exploration. Although there was variation between the leading edge and core, the greatest differences lay between males and females from core populations when exposed to a puff of air. We additionally investigated whether females would be less selective of a potential mate at the leading edge. We found marginal support for this and uncovered interesting details regarding P. manueli's mating system, wherein smaller females were more likely to mate than large ones. Overall, we found boldness and mating behaviour differences between the leading edge and core, but our data suggest greater differences lay between the sexes.