Geographic variation and body size differentiation in the medium-sized species of the genus Cybaeus (Araneae: Cybaeidae) in northern Kyushu, Japan, with descriptions of two new species

摘要

Distribution and geographic variation of the four medium-sized species of the genus Cybaeus (Araneae: Cybaeidae) collected from northern Kyushu, Japan, were examined in detail. They are C. kuramotoi, C. ashikitaensis, C. kokuraensis n. sp. and C. yufuin n. sp. Of these, Cybaeus kuramotoi has the widest distributional range covering most of western Japan. On the other hand, distribution of C. ashikitaensis is separated into two disjunct areas, Kyushu and eastern part of the Chugoku Mountains of Honshu. Cybaeus kokuraensis and C. yufuin are endemic to Kyushu and have very limited distributional ranges. Of the four medium-sized species, two or three species are often sympatrically found in northern Kyushu, although the kuramotoi-group and C. ashikitaensis are parapatric in Okayama and Hyogo Prefecture, western Honshu. There is a slight difference in body size and coloration between these species when they occur sympatrically.