Patterns and Processes of Diversification in Amazonian White Sand Ecosystems: Insights from Birds and Plants

White sand ecosystems (WSE) occur in nutrient-poor sandy soils patchily distributed throughout the lowlands of Amazonia. The diversification and current patterns of diversity of birds and plants specialized to the WSE were likely affected by abiotic conditions in very different ways relative to those in the upland Terra Firme forest, which has been more frequently studied over the years. Here, we review information on the geological origin of WSE substrates in Amazonia, and analyze current patterns of distribution of species and genetic diversity of plants and birds associated with these environments. Specifically, we analyze data on community composition to assess patterns of species diversity and turnover, and review and summarize published genetic data to unravel phylogenetic origins and phylogeographic patterns. Despite having lower species richness relative to other Amazonian ecosystems, the WSE present unique assemblages of species. The WSE are older than the Quaternary, yet their Pleistocene history has been dynamic, and the phylogenetic and population genetic patterns of the WSE taxa are consistent with this dynamism. The WSE were sensitive to Pleistocene climatic changes, likely undergoing lineage diversification and local extinctions. With increasing threats to Amazonian ecosystems, the low resilience of the WSE to disturbance needs to be factored into conservation management—particularly in the face of future climate change.