Abstract
Songbirds (oscine passerines) are the most species-rich and cosmopolitan bird group, comprising almost half of global avian diversity. Songbirds originated in Australia, but the evolutionary trajectory from a single species in an isolated continent to worldwide proliferation is poorly understood. Here, we combine the first comprehensive genome-scale DNA sequence data set for songbirds, fossil-based time calibrations, and geologically informed biogeographic reconstructions to provide a well-supported evolutionary hypothesis for the group. We show that songbird diversification began in the Oligocene, but accelerated in the early Miocene, at approximately half the age of most previous estimates. This burst of diversification occurred coincident with extensive island formation in Wallacea, which provided the first dispersal corridor out of Australia, and resulted in independent waves of songbird expansion through Asia to the rest of the globe. Our results reconcile songbird evolution with Earth history and link a major radiation of terrestrial biodiversity to early diversification within an isolated Australian continent.
Highlights
IntroductionSongbirds (oscine passerines) are the most species-rich and cosmopolitan bird group, comprising almost half of global avian diversity
Songbirds are the most species-rich and cosmopolitan bird group, comprising almost half of global avian diversity
We assembled contigs corresponding to 3,096–4,644 ultraconserved elements (UCEs) loci for each individual having an average length of 695.9 bp and average coverage of 47.9 Â
Summary
Songbirds (oscine passerines) are the most species-rich and cosmopolitan bird group, comprising almost half of global avian diversity. Revelation of a likely Gondwanan origin for all passerine birds[3,4,21] initiated a paradigm shift in biogeographic inquiry for the group and enabled an explicit timescale for passerine evolution based on geologic events during the breakup of the Gondwanan landmasses[2,3] Using these biogeographic calibrations and partially resolved molecular phylogenies, studies have identified key events in crown-oscine evolution[2,3,7,9,10], such as (1) a Palaeocene or Eocene origin in Australasia and early diversification of the Corvides among ‘proto-islands’ of New Guinea; (2) an African origin of the largest clade of Passerides via dispersal across the Indian Ocean from Australia; and (3) multiple Palaeogene long-distance dispersal events to Asia. Our biogeographic reconstructions support early songbird diversification in Australia in the Oligocene, followed by rapid diversification and geographic expansion via SE Asia early in the Miocene, coincident with extensive island formation in Wallacea
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