Systematics and biogeography of the shrike-babblers (Pteruthius): Species limits, molecular phylogenetics, and diversification patterns across southern Asia

Patterns of avian diversification in southern Asia are poorly understood due to the limited number of phylogenetic and biogeographic studies of endemic groups, mainly due to the dearth of recent tissue samples and a historical taxonomic bias underestimating avifaunal diversity. A systematic analysis of the endemic genus Pteruthius, the shrike-babblers, was undertaken in order to identify basal diagnosable taxa, analyze their phylogenetic relationships, and uncover patterns of diversification within southern Asia. Traditionally considered to be 5 species, a total of 19 distinct taxa of Pteruthius are diagnosable by fixed characters under the phylogenetic species concept—almost a four-fold increase in recognized diversity. Molecular phylogenetic analyses (85% of samples were from museum specimens) recovered a robust phylogeny that was largely congruent using parsimony, likelihood, and bayesian. Initial divergences in each major clade occurred in the early to mid-Pliocene, while the remaining majority of diversification events occurred in the Pleistocene. Within Pteruthius, timings of species divergences across similar geographic regions correspond to both single and multiple Earth history events, illustrating the complexities of continental diversification. A novel biogeographic pattern of species in peripheral areas (Java, W Himalayas, S Vietnam, Assam/Burma) diverging first from those in the core-mainland areas (E Himalayas, Yunnan, N Thailand, Indochina, Malay Peninsula) was uncovered.