Phylogeography of the Asian wood-feeding cockroach Salganea raggei Roth (Blattaria: Blaberidae) based on the mitochondrial COII gene

The mainland Asian species of the wood-feeding cockroach, Salganea raggei Roth, has the widest distribution range in the genus, extending from the eastern Himalayas to Taiwan. The phylogeny of S. raggei was studied in relation to its geographic distribution based on the complete mitochondrial cytochrome oxidase subunit II for 16 representatives collected from variable localities as well as the other Salganea species and outgroup taxa. The resultant phylogenetic tree showed the monophyly of S. raggei and, furthermore, revealed some intraspecific monophyletic groups for this species. It was also revealed that the ancestors of the Nepalese population (the westernmost one) separated from the others, the western Myanmar population (the second westernmost one) followed, and the remaining group split into three monophyletic groups. These results suggest that S. raggei originated around the westernmost part of the present distribution range and, thereafter, spread eastwards yielding derived populations. Preliminary calibration rates based on the COII transversion divergence suggested that the ancestors of S. raggei evolved following the collision between the Indian and Asian plates (~50 million years ago), and that each monophyletic group was formed from the middle of the Miocene to the Pliocene.