The roles of mating system and landscape topography in shaping the genetic population structure of the white-bearded manakin (Manacus manacus) in Trinidad, West Indies

Explaining the extent and causes of biotic distributions in a spatially explicit context is fundamental to our understanding of how organisms exist and evolve in natural environments. Yet, assessing the magnitude of effect that various biological and abiotic processes have on shaping intea-specific population structure remains a significant challenge. I determined the relative contributions of mating system and landscape topography in shaping the genetic population structure of a classically-lekking Neotropical forest bird, the White-bearded Manakin (Manacus manacus; Pipridae). Using a patented technology able to genotype ostensibly dominant Amplified Fragment-Length Polymorphism (AFLP) markers, I screened 824 manakins sampled from 42 leks in Trinidad, West Indies for genetic polymorphisms. Analyses of codominant markers obtained from 356 loci indicated significant variability in terms of the proportion of polymorphic nucleotide sites and degree of heterozygosity. The magnitude of interlek genetic differentiation within montane and lowland habitats was considerable, but very little differentiation was evident between the two habitats. In both habitats, observed patterns of differentiation were inconsistent with a two-dimensional isolation-by-distance model. However, manakins in montane regions exhibited slightly more within-population differentiation than did those sampled from the flat lowlands. Overall, this study showed that lek proximity and landscape topography were not indicative of any general pattern of genetic structure, but rather such differentiation results from adult male treating success. I conclude that a demographic scouting-recruitment-dominance process is responsible for the genetic population structure observed in Trinidadian White-bearded Manakins and at the scale analyzed, independent of landscape topography.