Phylogeny of the Southeast Asian freshwater fish genus Pangio (Cypriniformes; Cobitidae).

The genus Pangio is one of the most species-rich of the loach family Cobitidae and widespread across South and Southeast Asia. Its species diversity has never been studied under a clear phylogenetic approach, but four 'species-groups' were proposed according to the most obvious morphological characters. We present here phylogenetic analyses of the genus Pangio based on sequence data of the mitochondrial cytochrome b gene, the nuclear recombination-activating gene 1 (RAG 1) and a combined dataset of 109 specimens from 18 morphologically identified species across the whole distribution area of the genus. Our data reveal the existence of three major lineages within Pangio. Two of our major lineages were congruent with formerly proposed species-groups, the remaining two species-groups together formed the third major lineage; herein we refer to the lineages as to anguillaris-group, kuhlii-oblonga group and shelfordii-group. The application of a molecular clock dated the age of the three lineages to 33-29 million years. At the species level, our data suggest about 30 distinct lineages, indicating that there is a high number of undescribed species within Pangio. The use of Pangio to address biogeographic questions is demonstrated with the example of the shelfordii-group, which is distributed across Sundaland.