Impacts of the social environment on male sexual behavior and attention allocation

Abstract

Social communication occurs within a network and interactions between individuals rarely occur in private. The presence of observing individuals have been shown to affect the behavior of a signaling individual, however there are many aspects of a complex social environment that are still not well understood. My thesis assessed effecrs of the social environment on the mating behavior and attention allocation of male sailfin mollies (Poecilia latipinna), a livebearing freshwater fish. Sailfin mollies lives in sympatry with the gynogenetic Amazon molly (Poecilia Formosa), which requires the sperm of a heterospecific to begin embryogenesis. Male sailfin mollies can distinguish between conspecific females and Amazon mollies, but do receive indirect fitness benefits from copulations with Amazon mollies in cases of conspecific female mate choice copying. The use of this sexual-asexual mating system in these studies provides another interesting component of the social environment and may help elucidate ways in which Amazon mollies receive copulation opportunities. In this thesis, I addressed effects of rival male audience size on sexual activity and attention allocation toward a conspecific female or heterospecific Amazon female. Additionally, I looked at how the species of a female audience (conspecific or heterospecific) altered sexual behavior and attention division toward a conspecific female or heterospecific Amazon female. I did not find any significant changes to male sexual behavior in the presence of a male audience of varying body size while partnered with either a conspecific of heterospecific female. However, in the presence of a female audience, I did find significant effects of stimulus female species, as males displayed more behaviors toward conspecific stimulus females but there was no effect of the species of the audience female. This result confirms previous findings that male sailfin mollies both distinguish between and prefer conspecific females over heterospecific females but also shows that current interactions influence behavior more than possible future interactions. Due to my experimental design, my study closely replicated events that would occur in complex social situations in nature, so my results could be due in part to limits on cognitive load. In my study of attention allocation, I found that in both cases, males direct more attention toward a stimulus female regardless of female species or male audience, but direct more attention towards conspecifics overall. In addition, the species of the female audience also significantly influenced how male attention was divided, which may be due to anticipation of future copulation opportunities. I also found that focal male size is important in attention allocation and follows predictions of perceived sperm competition risk based on relative body size. The results provided by this study show that attentional division is not determined by one factor alone, but rather several components of the social environment in which an individual interacts. Overall, my thesis highlights the importance of social context in influencing behavior and dividing an individual’s attention in mating situations.