Character displacement and evolution of the Japanese Mnais damselflies (Zygoptera: Calopterygidae)

Arguments are presented for the 3 generally recognized taxa of the genus Mnais Selys occurring in the Japanese Islands to be regarded as independent spp., viz. M. costalis Selys, M. pruinosa Selys, and M. nawai Yamamoto. It is pointed out that the M. pruinosa populations occurring in central Honshu (the Setouchi Group) are also possibly an independent sp. to be distinguished from those occurring in southwestern Japan (the Nankai and Saikai Groups). Essentially the same combination of forms (a heterochromatic orange-winged, occasionally pale-orangeor dark-brown-winged male, a homoeochromatic hyaline-winged male, and a homoeochromatic hyaline-winged female) seems to occur in most districts of the Japanese Islands. Based on the taxonomic arrangement of the known forms, the evolution of the Japanese Mnais spp. is discussed. The present geographic distribution of the taxa and the combination of forms in various districts are interpreted by a working hypothesis based on the so-called "competitive exclusion (or displacement) principle" and a consequent "character displacement”.