Molecular phylogenetics and diversification within one of the most geographically variable bird species complexes Pachycephala pectoralis/melanura

The golden-mangrove whistler complex Pachycephala pectoralis/melanura is, with 66 named populations, described as the most complex avian example of geographic variation in the World. It represents a well-known example of niche differentiation where one species P. pectoralis is found on faunistically rich larger islands (and mainland) and the other P. melanura is confined to adjacent, faunistically poor islets. Except for a comparison of some Solomon Island populations, the relationships among these taxa have not been tested using molecular data. Here we combine a dense taxon sampling (22 populations of 12 named taxa distributed east of New Guinea and in Australia), with molecular data (two nuclear and two mitochondrial markers) to unravel more of the evolutionary history behind the golden whistler complex. In particular we examine relationships between Pachycephala melanura, and the very similar-looking P. citreogaster (Bismarcks Islands) and P. pectoralis (Australia). We demonstrate that a well-supported group of golden whistlers inhabit the Bismarck Islands and that several small islets in the immediate vicinity are inhabited by another monophyletic group consisting of P. melanura, mangrove golden whistler.