Systematics and biogeography of the ant genus Crematogaster Lund subgenus Orthocrema Santschi in Asia (Hymenoptera: Formicidae)

The subgenus Orthocrema of the ant genus Crematogaster is a well defined group and diverse in the tropical Asia. Its systematics has remained poorly understood because of a lack of modern revisionary work. Crematogaster (Orthocrema) is revised for the Asian region, and 27 species including ten new species are recognized. Five species groups: the C. baduvi group (4 spp.); the C. binghamii group (3 spp.); the C. biroi group (10 spp.); the C. moatensis group (1 sp.); the C. quadriruga group (9 spp.) are established based on worker caste morphology. A key to Asian species of the subgenus Orthocrema based on the worker caste is given. Phylogenetic relationships of Asian Orthocrema are analyzed. The analysis revealed that the C. baduvi-, C. binghamii-, and C. biroi groups are monophyletic, and that the allopatric distribution patterns of closely related species imply that Asian Orthocrema is composed of relatively young taxa. There have been at least three west-to-east dispersal events across Wallace's line in the C. baduvi-, C. quadriruga- and C. biroi groups.