Molecular evidence suggests radical revision of species limits in the great speciator white-eye genus Zosterops

White-eyes (Zosterops spp.) are a group of small passerines distributed across the Eastern Hemisphere that have become a textbook example of rapid speciation. However, traditional taxonomy has relied heavily on conservative plumage features to delimit white-eye species boundaries, resulting in several recent demonstrations of misclassification. Resolution of confused taxonomy is important in order to correctly delimit species and identify taxa which may require conservation, particularly in Asia where the songbird trade is decimating wild populations. In this study, we aim to untangle multiple instances of confused taxonomic treatment in three large, widespread Asian wastebasket species complexes of white-eye (Oriental White-eye Zosterops palpebrosus, Japanese White-eye Zosterops japonicus and Mountain White-eye Zosterops montanus) renowned for their conservative morphology. Using mitochondrial DNA from 173 individuals spanning 42 taxa, we uncovered extensive polyphyly in Z. palpebrosus and Z. japonicus and propose some radically revised species limits under which former members of Z. palpebrosus and Z. japonicus would be reassigned into four and two different species, respectively. The revised taxonomy results in a net loss of two previously recognized species and a net gain of two newly recognized species, leading to significant taxonomic change but a lack of additional species-level diversity. One of the newly elevated species, Zosterops melanurus from Java and Bali, is also the world's most heavily traded songbird and requires urgent conservation attention.