Reproductive behaviour of male Xylocopa virginica and the influence of body size, nestmates, and siblings on territory defence

Abstract

Males of Xylocopa virginica are territorial like many other bee species. Males interact aggressively to displace other males from territories. Body size is known to influence resource holding potential in many other taxa, and studies of bees suggest that body size is important for territorial males. Familiarity and the avoidance of kin competition are also known to influence territorial behaviours in other taxa but has not been studied in male bees. Recent evidence suggests that nestmate recognition occurs in X. virginica and there is also evidence for the avoidance of kin competition. This thesis tests whether body size, familiarity, and kinship influence territorial interactions using social networking tools. Around half of all males attempted to establish or defend a territory. Males that established or defended territories are larger than males that did not. Male body size has a weak positive influence on hover rates, related to holding territories, the number of hovering neighbours each male had, and the number of males each male chased or fled in defence of territories. I found no evidence to support that familiarity influences aggressive behaviours, but there is a strong correlation with the number of neighbours a male had and the number of males it chased or fled. Brothers estimated from microsatellite genotypes are no more aggressive to each other than to non-siblings. However, the results indicate that several sets of brothers overwintered in different nests, which does not coincide with the behavioural patterns described in the literature. This study is the first step towards understanding the influence of familiarity and kin competition on male behaviour in a taxonomic group with a wide array of mate-locating strategies. Discussed herein are the importance of continued research on mating systems and mate-locating strategies of bees, as well as outlining future projects to address several gaps in knowledge that remain after this study.