Unexpected Feature of the Lepidoptera Assemblages on the Small Shelf Islands in the Peter the Great Gulf (Sea of Japan, South of Russian Far East)

Abstract

The article describes and discusses unexpected feature of agrological structure of the moths' species assemblages on four small shelf islands in the Peter the Great Gulf (Sea of Japan, south of Russian Far East). Before insect fauna of these islands was almost unknown. The study was conducted according to standard entomological procedures of insect collecting and chorological analysis of local faunas. Statistical analysis was performed using the detrended correspondence analysis. Typification of areas was made following the principles by Gorodkov. As a result, it was found that geometrid fauna demonstrates high degree of patchiness between the islands and species richness at times lesser than in neighboring continental localities. Nevertheless, a high similarity of agrological structure of the moths inhabited the islands and the continental localities was explored. This is unexpected because of low species richness of geometrids on the islands and their mosaic distribution between them, being original current climatic conditions on the islands and their separation from mainland at beginning of Holocene in different climatic epoch. Starting from the theory of island biogeography, and taking into account geography of the gulf, this fact could be explained by assuming that the moths on the islands represented mainly by resident populations, which occasionally, but regularly over long time intervals, are replenished by random immigrants from mainland. This random immigration could alignment of areological structure of moths between islands and mainland. This model could explain both a high degree of patchiness of the species composition of the moths on the islands, as well as a high degree of compliance of their arealogical structure to neighboring continental localities. However, this hypothesis assumes an equivalence of distribution of migratory ability of moths in large arealogical groups, which requires special research.