Supermatrix Phylogenetic Tree of Passerine Birds From the Indo-Australian Archipelago Highlights Contrasting Histories of Regional Endemism

The Indo-Australian Archipelago (IAA) is a biodiversity hotspot characterized by high levels of biotic endemism and turnover. Explanations for these biodiversity patterns tend to focus on the role of the complex and dynamic geological history of the region. However, it is only in the last decade that large-scale phylogenetically informed analyses of macroevolutionary dynamics across the region have become feasible. A recent study of bird distributions and diversity across the archipelago highlighted marked turnover of species across geographically proximate areas in the IAA and the overarching role of sea barriers in shaping turnover. To build on this work and better understand the relative histories of bird diversification in the different areas of the IAA, we compile an updated and as-complete-as-possible supermatrix phylogenetic tree for passerine birds from the region and use this to estimate and compare levels of endemism in different areas of the IAA. This genetic framework further emphasizes contrasting histories of diversification in different areas of the archipelago. As expected for this clade, we found that Australia is consistently inferred as a hotspot of paleoendemism, the islands of East Melanesia and possibly Maluku are characterized by neoendemism, while the world's largest and highest tropical island, New Guinea, is inferred to be a center of superendemism, that is, both paleo- and neoendemism. Our updated tree also highlights a significant increase in the number of recognized bird species across the IAA in the last 10 years, as well as improved completeness of genetic sampling.