Genetic evidence for the recognition of two allopatric species of Asian bronze featherback Notopterus (Teleostei, Osteoglossomorpha, Notopteridae)

The fish genus Notopterus Lacepède, 1800 (Notopteridae) currently includes only one species, the Asian bronze featherback Notopterus notopterus (Pallas, 1769). This common freshwater species is widely distributed in the Oriental region, from the Indus basin in the west, the Mekong basin in the east and Java Island in the south. To examine the phylogeographic structure of N. notopterus across its range, we analysed 74 publicly available cytochrome oxidase I (COI) sequences, 72 of them determined from known-origin specimens, along with four newly-determined sequences from Peninsular Malaysian specimens. We found that N. notopterus is a complex of two allopatric species that diverge from each other by 7.5% mean p-distance. The first species is endemic to South Asia (from Indus basin to Ganga-Brahmaputra system), whereas the distribution of the second species is restricted to Southeast Asia. The exact limit between the distributions of these two species is not known, but it should fall somewhere between the Ganga-Brahmaputra and Salween basins, a region already identified as a major faunal boundary in the Oriental region. The name N. notopterus is retained for the Southeast Asian species, while the name Notopterus synurus (Bloch & Schneider, 1801) should be applied to the South Asian species. A comparative morphological study is needed to reveal the degree of morphological differentiation between the two species.