This project investigates the relationship between spatial structure, genetic relatedness and reproductive skew in a set of closely related species of manakins (Aves: Pipridae) that exhibit lekking behavior in Neotropical wet forests. Lekking behavior, which occurs in many animal taxa, is characterized by a aggregation of males displaying for females in traditional locations and a lack of association between males and females after copulation. Females visit leks only to breed and rear their young elsewhere without assistance from the male. Lekking behavior often results in large reproductive variance (skew) among males because usually only one or a few males at the lek sites successfully copulate with females. Manakins represent a model system to investigate reproductive skew because (1) birds are common inhabitants of understory of tropical wet forests, (2) six closely related species occur in the same geographic location and thus experience similar environments, and (3) species differ in lek organization (e.g., number of males and distance among males at leks) and lekking behavior, characters key for predicting reproductive skew and analyzing population genetic consequences of lek mating systems. Considerable theory regarding reproductive skew has emerged, but there yet exist few empirical tests. Understanding the factors that influence reproductive skew is essential to understand the evolution of lekking behavior, a mating system that has evolved in a number of taxa and that has received a great deal of attention in theoretical and empirical literature. Measures of reproductive skew in lekking species are often based on observations of copulations at the lek. Yet, paternity analyses using molecular genetic data have revealed that for a number of bird species observations may provide misleading results about paternity. In the proposed study, observational data at leks are combined with direct measures of individual male success and reproductive skew through paternity analyses of offspring found at nests. This research will be the first to compare lekking behavior and its genetic consequences among a set of closely related species that occur in the same forest but that vary in lek organization and spatial structure. Such an approach should contribute substantially to our understanding of the evolution of lek mating system. The proposed research also effectively combines the ecological, behavioral, and molecular genetic expertise of the principal investigators and provides an avenue for new collaborative research that will enhance research programs of each senior investigator. Field and laboratory components of the research program will provide key opportunities for students from both the home institution and from Ecuadorean universities to gain research experience. Several Ecuadorean and UM-St. Louis students are expected to expand on aspects of the proposed project as part of their thesis or dissertation research. Travel expenses in Ecuador incurred by UM-St. Louis students and faculty will be supported by the NSF OFfice of International Science and Engineering.
