Doctor of Philosophy
Date of Defense
John G. Blake
The importance of climatic and geologic factors as drivers of population differentiation and speciation in the Neotropical region has long been appreciated. However, many questions remain regarding their roles underlying the processes and patterns of diversification. Studies conducted in distinct regions containing a suite of geological and ecological conditions constitute ideal scenarios to assess the role of Pleistocene climatic changes, rivers, and mountain building as historical diversification mechanisms. In chapters 1 and 2, I used an integrative approach combining molecular phylogenetics, phylogeography and population genetics to elucidate the importance of climatic and geological factors as engines of diversification. I focused on the South American fire-eye antbirds (genus Pyriglena), which occur in forested areas in southeastern Amazonian basin, Pantanal basin, Andes and Atlantic Coast. My study suggests that fire-eyes represent a young and rapid diversification in South America. It is conceivable that the origin of the major clades in this group trace back to the formation of the modern course of large rivers in the Amazonian basin and Atlantic Forest, with subsequent diversification fostered by more recent Pleistocene climatic oscillations creating opportunities for range expansion and geographic isolation in the Andes, Pantanal and Atlantic Forest. However, the role of large rivers as historical barriers to dispersal was apparently stronger in the Amazon basin relative to western South America (western lowlands and Andes) and Atlantic Forest. On the other hand, climatic oscillations seemed less important in creating opportunities for geographic differentiation within the Amazon comparative to the other regions. Fire-eyes seemed to have a complex history of diversification, involving large-scale geological and climatic processes acting over regional and continental scales during the last ~ 2.5 Mya. In chapter 3, I examined in detail how songs varied across the range of Atlantic Forest fire-eye antbirds, and I tested several different hypotheses of the origin of song divergence in an attempt to explain their current vocal variation. Genetic differentiation and introgressive hybridization seemed to explain the overall song variation and geographic structuring in fire-eyes better than alternative factors such as body size, bill morphology and ecology.
Coelho, Marcos Maldonado, "Evolution and biogeography of fire-eye antbirds (genus Pyriglena): Insights from molecules and songs" (2012). Dissertations. 364.