Relationship between Chromosomal Races/Subraces in the Brachypterous Grasshopper Podisma sapporensis (Orthoptera: Acrididae) Inferred from Mitochondrial ND2 and COI Gene Sequences

Podisma sapporensis Shiraki, 1910 (Orthoptera: Acrididae) is distributed on the islands of northern Japan and Far East Russia (Hokkaido, Sakhalin, and Kunashiri), and it exhibits a unique diversity of chromosomal races (X0 and neo-XY) on the island of Hokkaido. To infer the history of geographical isolation and chromosome rearrangements (main races and subraces), we used mitochondrial DNA (mtDNA) sequence variation in two regions, NADH dehydrogenase subunit 2 (ND2) and cytochrome oxidase subunit II (COII), among 55 individuals representing eight X0/XX and three neo-XY/XX populations. The molecular phylogenetic tree revealed a high level of overall mitochondrial diversity, but the clustering of the examined population is in most cases closely related to their geographic distribution and associated with chromosomal races and subraces. Together with cytogenetic observations, we discuss the origin of the polymorphism within the X0 and XY races as well as differences between both northern and eastern races.