Geographic drivers of avian diversification in the Philippine archipelago

Abstract

I investigate the relative roles of different classes of geographical barriers in the diversification of the Philippine avifauna, by inferring the evolutionary relationships of 20 avian groups with DNA sequence data. In chapter one, I reconstruct the historical biogeography of the Aethopyga sunbirds. In chapter two, I examine the distribution of genetic variation and plumage patterns in Robsonius ground-warblers, and described a new species. In chapter 3, I reconstruct the evolutionary history and ecological niches of eight co-distributed polytypic species of Philippine birds, and infer that a paleoclimate barrier dove diversification. In chapter four, I use molecular markers and plumage characters to reassess conservative species limits in 19 avian species or species groups in the Mindanao Island group of the Philippines. In addition to permanent marine barriers, long understood to isolate insular lineages, I provide evidence that periodic marine barriers, periodic climatic barriers, and complex topography isolate and promote diversification in Philippine birds. Populations inhabiting island groups (bounded by deep-water barriers) are frequently paraphyletic, contrary to the perception that deep-water barriers are the most important geographic isolating feature in insular systems. I document two small avian radiations, the Robsonius in Luzon, and Aethopyga in Mindanao, are exceptions to the paradigm that birds do not diversify within single islands. Congruence of molecular markers and plumage characters support that avian taxonomy in the Philippines is extremely conservative, and most Philippines species would be more appropriately treated as sets of allopatric evolutionary lineages, rather than widespread polytypic species.