Molecular phylogeny and geographic distribution of wood-feeding cockroaches in East Asian islands

Molecular phylogenetic relationships of the wood-feeding cockroach genera S alganea and Panesthia (Blaberidae; Panesthiinae) in East Asian Islands (Ryu kyu archipelago and Taiwan Island) were analyzed based on the DNA sequence of the complete mitochondrial cytochrome oxidase II gene. Unweighted parsim ony analysis resulted in high bootstrap support; for relationships within P anesthia taxa; however, some nodes were unresolved between members of Salga nea. Comparison of the number of transitions and transversions with genetic distance at each codon position suggested that saturation of third-codon s ubstitutions has occurred between certain pairs of taxa. Consequently, diff erential weighting of substitutions at these sites was performed, which res ulted in a substantial increase in resolution of Salganea relationships. Th e inferred phylogenies for both genera displayed good correspondence to the geographical locations of populations but however did not agree with previ ous subspecies designations based on morphological characters. It appears t hat both cockroach genera invaded the Ryukyu archipelago from the Taiwan re gion via a land-bridge present in the Miocene period. Invasion of the main islands of Japan by these cockroaches most likely occurred before the forma tion of the Tokara Tectonic Strait. Our study suggests that several barrier s to gene flow have arisen and persisted over the past similar to 10 millio n years, which have caused segregation and vicariant speciation of the cock roach taxa of this region. (C) 1999 Academic Press.