Taxonomic revision of Mecyclothorax Sharp (Coleoptera, Carabidae) of Hawaii Island: abundant genitalic variation in a nascent island radiation

Abstract

The Hawaii Island fauna of Mecyclothorax Sharp, 1903 is taxonomically revised and found to comprise 30 species, 18 newly described: M. gagnei sp. n., M. nitidus sp. n., M. maunakukini sp. n., M. punakukini sp. n., M. kaukukini sp. n., M. perivariipes sp. n., M. aa sp. n., M. giffini sp. n., M. hephaestus sp. n., M. funebris sp. n., M. granulipennis sp. n., M. rufipennis sp. n., M. blackburnianus sp. n., M. swezeyi sp. n., M. sinuosus sp. n., M. williamsi sp. n., M. purpuripennis sp. n., and M. footei sp. n. New synonymies include: Mecyclothorax parvus Britton, 1948 = M. subunctus (Perkins), 1917; Thriscothorax munroi Perkins, 1937 = M. karschi (Blackburn), 1882; Thriscothorax gracilis Sharp, 1903 and Mecyclothorax proximus Britton, 1948 = M. konanus Sharp, 1903; Mecyclothorax terminalis Britton, 1948 = M. discedens (Sharp) 1903. Mecyclothorax vulcanus (Blackburn) was described from a mixed series, with the cryptic sibling species M. hephaestus newly described to correct the partial misidentification. Species delimitation for the highly variable M. konanus is achieved using a hierarchical analysis based on infraspecifically variable attributes. Extensive male genitalic variation is documented within M. konanus and M. deverilli (Blackburn), and also among the cryptic sibling species pair M. variipes (Blackburn) and M. perivariipes. The observed variation is consistent with various hypotheses of sexual selection, but not with the genitalic lock and key hypothesis. Areas of endemism are tentatively proposed based on the most restricted distributions of Hawaii Island Mecyclothorax, with various flanks of Mauna Kea and Mauna Loa volcanoes identified as distinctive areas. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)