The radiation of Austral teals (Aves: Anseriformes) and the evolution of flightlessness

The origin and evolution in the Southern Hemisphere of the Austral teals, consisting of the grey-teal and brown-teal species complexes, remains poorly understood owing to limited molecular data. With the group containing multiple independent examples of flight loss, understanding the evolutionary history of the group is of significant interest for functional genomic studies into the evolution of flightlessness. Here, we present the first whole-mitogenome-based phylogeny of the Austral teals. We show that the group diverged from a common ancestor with mallards in the late Miocene and soon after radiated into the brown-teal and grey-teal lineages, in addition to the widely distributed pintails and green-winged teals. The brown-teal species complex, which includes the volant brown teal, the flight-impaired, sub-Antarctic Auckland Island teal, and the flightless, Chatham Island and sub-Antarctic Campbell Island teals, radiated within the past 0.9–1.8 Myr. The divergence of the extinct Chatham Island teal and the colonization of the Auckland and Campbell Islands occurred from mainland New Zealand. Morphological changes towards flightlessness are also present in the volant brown teal on mainland New Zealand, suggesting that this group was on the pathway to flightlessness, a trend that accelerated in some insular island lineages.