A gang of thieves -- evolution of cooperative kleptoparasitism in the subfamily Argyrodinae (Araneae: Theridiidae)

Abstract

This is the first comprehensive study of group-living behavior in kleptoparasitic Argyrodinae, and the first species level molecular phylogenetic analysis of the Argyrodinae (Araneae: Theridiidae). I included four research chapters in this dissertation. In Chapter 2, I showed the first empirical study of cooperative kleptoparasitism in Argyrodes miniaceus. The results showed that, at least at the level of foraging, group-living behavior has adaptive function of cooperation. Using a game theory model, the payoff of being cooperator in a group is greater than the payoff of being solitary. In Chapter 3, I concluded that kleptoparasites do not aggregate simply because the webs are large and can support multiple kleptoparasites. Social interactions among group members provide additional benefits that favor individuals remaining in groups. In Chapter 4, I concluded that group members could gain indirect benefit of fitness by cooperating with group members, who are potentially related individuals. This is because in group-living Argyrodes, group members are significantly more closely related than the individuals drawn randomly from the population in a small geographic scale. In Chapter 5, the phylogenetic analyses showed several independent origins of group-living behavior in different species groups. The evolutionary sequence of foraging strategies of Argyrodinae is from free-living to araneophagy, then to kleptoparasitism. The comparative analyses showed the specialization to large host is correlated with the evolution of group-living behavior. In addition, the processes of specialization thus becoming group-living may have caused diversification within species groups.