Phylogeny, Biodiversity, and Species Limits of Passerine Birds in the Sino-Himalayan Region—A Critical Review

We analyzed passerine biodiversity and phylogeography in the Sino-Himalayan region with respect to neighboring areas, especially the Siberian taiga zone to the north and tropical Asia southeast of the Himalayas and mountainous parts of southwest China. Fresh results, informative about evolutionary processes in that area, were obtained mainly by the application of new methods in passerine systematics, acoustic and molecular genetic markers. It became evident that species with areas in the Himalayas and southwest China and, in addition, often with disjunct areas in Siberia, actually belong to swarms of closely related, mostly allopatric species. In many cases these differ markedly in vocalizations and are deeply split according to molecular genetic markers. External morphology of the constituent taxa quite often remained surprisingly homogeneous and thus resulted in traditional subspecies status of single populations at best. Other such well-differentiated taxa were often overlooked and only discovered by m...