Reproductive and Social Dynamics of a Lek Breeding Bird

by Ryder, Thomas Brandt

Sociality and the unequal apportionment of reproductive success among social individuals is a common characteristic of many vertebrate taxa. To date, our understanding of what factors drive high variance in reproductive success (i.e., intra vs. inter-sexual selection) and which male attributes contribute to that variance, are still fragmentary for most species. Moreover, how social structure interacts with individual behavior and fitness remains understudied despite its potential importance to the evolution of cooperation. This dissertation research focused on understanding this complex synergistic interplay between social and reproductive dynamics in a lekbreeding bird, the wire-tailed manakin. The first chapter examines the complex display ritual of this species of manakin (Pipra filicauda). More specifically, it quantifies and compares the frequency of individual behavior among males of different age and social status. In addition, the first chapter examines in detail the genetic relatedness of male partnerships to test the kin selection hypothesis. The second chapter uses these complex reticulate interactions to build social networks. This chapter details the emergent properties of these networks and examines their role in determining male social ascendancy and access to reproduction. The third chapter uses a combination of molecular tools and network analysis to create a synthetic understanding of variance in male reproductive success. This chapter presents molecular estimates of reproductive skew and examines the social correlates of male reproductive success. Our primary results show 1) that males within leks are not more related than expected by chance, enabling us to reject the role of kin selection in the lek evolution of wire-tailed manakins; 2) that the complex networks of social interactions among males contain the 3 ingredients needed for the evolution of cooperation; 3) that social connectivity of young males was predictive of their later social ascendancy; 4) that the number of male affiliations was strongly predictive of the number of offspring he sired. Overall our findings greatly advance our understanding of social relationships and the role they play in the evolution of cooperation and reproductive variance. 4