The major diversification of songbird species began about 23 million years ago and was associated with the formation of islands providing a route out of Australia, according to a study published in Nature Communications this week. Previous studies had suggested that songbirds must have dispersed across thousands of kilometers of ocean to leave Australia.
Approximately 5,000 species of songbirds (collectively known as oscine passerines) are distributed across the world. The ancestor of the songbirds has been traced back to Australia, but competing theories have been proposed for when songbird species diversified and how they dispersed out of Australia.
Robert Moyle and colleagues combined genomic, fossil, and biogeographic data to reconstruct the species and geographic radiation of the songbirds. They found that the songbird radiation coincided with the tectonic collision and uplift of Wallacea, a group of islands bridging Australia and Asia, around 23 million years ago. This timeframe for dispersal is more recent than previously thought.
These findings reconcile the evolutionary and biogeographic history of songbirds with geological history.