Historical biogeography of an Indo-Pacific passerine bird family (Pachycephalidae): different colonization patterns in the Indonesian and Melanesian archipelagos

Aim We use molecular-based phylogenetic methods and ancestral area reconstructions to examine the systematic relationships and biogeographical history of the Indo-Pacific passerine bird family Pachycephalidae (whistlers). Analysed within an explicit spatiotemporal framework, we elucidate distinct patterns of diversification across the Melanesian and Indonesian archipelagos and explore whether these results may be explained by regional palaeogeological events. We further assess the significance of upstream colonization and its role in species accumulation within the region. Location The Indo-Pacific region, with an emphasis on the archipelagos on either side of the Australo-Papuan continent. Methods We used three nuclear and two mitochondrial markers to construct a molecular phylogenetic hypothesis of the Pachycephalidae by analysing 35 of the 49 species known to belong to the family. The programs diva and MRBAYES were used to reconstruct ancestral area relationships and to examine biogeographical relationships across the family, and beast was implemented to assess the timing of dispersal events. Results We constructed a molecular phylogenetic hypothesis for the Pachycephalidae and estimated divergence times and ancestral area relationships. Different colonization patterns are apparent for the Pachycephalidae in the Indonesian and the Melanesian archipelagos. The Indonesian archipelago was colonized numerous times, whereas one or two colonizations of the Melanesian archipelagos account for the entire diversity of that region. After initial colonization of the Melanesian archipelagos some whistler species recolonized Australia and may have commenced a second round of colonization into Melanesia. Main conclusions The contrasting dispersal patterns of whistlers in archipelagos on either side of the Australo-Papuan continent are congruent with the arrangement and history of islands in each of the regions and demonstrate that knowledge of palaeogeography is important for an understanding of evolutionary patterns in archipelagos. We also highlight that recolonization of continents from islands may be more common than has previously been assumed.