Biogeography and Population Genomics of Amazonian White-sand Ecosystems Birds

Amazonia is the most biologically diverse region of the planet and the source of this diversity has long intrigued evolutionary biologists and naturalists. Although Amazonia was seen for a long time as a stable region, more evidence has been gathered showing that the landscape and climate have been dynamic in the region. Geological and climatic events had varying levels of importance in driving diversification for each particular Amazonian ecosystem and its associated species. Species occurring in the same ecosystem can thus be hypothesized to share a common evolutionary history. In this thesis I investigate the evolutionary history and population genomics of birds specialized in the Amazonian white-sand ecosystems (WSE). The WSE occur patchily across the Amazonian region in nutrient poor and seasonally flooded sandy soils. These soils can have different ages spanning several geological periods and have multiple origins. Strong ecological filtering appears to affect community composition and phylogenetic structure of WSE communities. In birds the ecological filtering resulted in a phylogenetic overdispersed community of specialist species and impoverished assemblages in small and isolated fragments. Bird species adapted to WSE show ample variation in range sizes. This variation is partially explained by their dispersal capability, using the hand-wing index as a proxy. Better dispersers have bigger range sizes, a pattern probably driven by the fragmented nature of WSE, which makes it harder for poor dispersers to reach new patches and expand their ranges. Some of the WSE birds have a relatively old origin in the Miocene-Pliocene periods, while population genetic patterns are shallow and recent, possibly dating back to the Late Pleistocene. Seven studied WSE birds showed variable amounts of shared population genomic structure, as idiosyncrasies also were observed. The Amazon river is an important geographic barrier for WSE birds. Stronger genetic structure was observed in southern Amazonia, while in the north there was shallower population structure and more idiosyncratic patterns. The climate fluctuations in the Pleistocene appear to have affected the genetic diversity of WSE bird species, specially the last glacial cycle, generating the relatively shallow geographic structure observed across Amazonia.