Revision of the fungivorous genus Oxyporus (s. str.) (Coleoptera: Staphylinidae: Oxyporinae) of Japan, with preliminary analysis of host relationships, species richness and zoogeography

Abstract

Summary: The Japanese members of the genus Oxyporus (s. str.) are revised. Eleven species are recognised as follows: O. rufus (Linnaeus, 1758) [O. tosensis Takeuchi, 1941, n. syn.; O. rufus osawai Nakane & Sawada, 1956, n. syn.], O. maxillosus Fabricius, 1793 [O. kobayashii Hayashi, 2015, n. syn.], O. niger Sharp, 1889, O. japonicus Sharp, 1889, O. triangulum Sharp, 1889, O. parcus Sharp, 1889, O. maculiventris Sharp, 1889 [O. aokii R. Dvořák, 1956, n. syn.], O. imitator Nakane & Sawada, 1956, O. crocatus Fauvel, 1901 [O. lewisi basicornis Cameron, 1930, n. syn.], O. germanus Sharp, 1889, and O. basiventris Jarrige, 1948. Lectotypes of O. japonicus Sharp, 1889, O. parcus Sharp, 1889, O. maculiventris Sharp, 1889, O. crocatus Fauvel, 1901 and O. lewisi Cameron, 1930 are designated. All species are redescribed with illustrations of the taxonomically important characters and photographs of the habitus. An identification key for Japanese Oxyporus (s. str.) species is provided. Oxyporus maxillosus is recorded from Rishiri-tô island for the first time as the first representative of the genus from the island. Furthermore, O. imitator is newly recorded from Shikoku and Kyushu. Host fungi information is contributed. Analyses based on the information revealed the low host similarities among species. The study also tests the distribution patterns of each species and the faunistic endemism within Japan, based on the taxonomic framework constructed herein. It elucidated the following: (1) faunal distinctions exist between Hokkaido and south of the Honshu; (2) 10 species are sympatrically distributed in Honshu and Shikoku, and nine in Kyushu; (3) although species richness in Japan is highest in Far East Asia, only O. imitator is endemic; (4) the region with highest similarity to Japan is calculated to be the Korean Peninsula. A comparison of Oxyporus fauna across the regions of East Asia suggests that it is necessary to conduct further comprehensive taxonomic studies. Additionally, it is hypothesised that multiple Japanese Oxyporus species can occur sympatrically because of the existence of reproductive isolation due to differences in the hosts used. A checklist of the Oxyporinae of the World is provided in the appendix.