Taxonomic revision of the Mecyclothorax beetles (Coleoptera: Carabidae) of Oahu: epithets as epitaphs for an endangered fauna?

摘要

The Mecyclothorax Sharp beetle fauna of Oahu, Hawaii is revised, including the description of 13 new species-M. acherontius, M. uncinus, M. lobatus, M. dentatus, M. calceus, M. euryoides, M. invictus, M. ovatulus, M. lemur, M. satyrus, M. ramsdalei, M. pelops and M. niobe spp.n.-to complement the six previously described species. Several cryptic species complexes characterized by similar external anatomy and highly divergent male genitalia are present in the fauna, including the M. brevis (Blackburn) species complex-four species sympatrically distributed on Tantalus, a mountain on the northern margin of Honolulu-and the sympatric sister species M. carteri (Perkins) and M. invictus from Mt. Kaala in the western Waianae Range. This repeated pattern of closely related species characterized by divergent male genitalia and relatively static external anatomy is also observed in the Mecyclothorax fauna of Molokai, an island of moderate geologic age within the Hawaiian archipelago, but not in the Mecyclothorax fauna of the most recently emergent Hawaii Island. Species distributions are generally also much more restricted on the older islands. These results are consistent with the occurrence of rampant, unfixed infraspecific genitalic variation early in an island radiation, with subsequent fixation of divergent genitalic characters occurring as speciation proceeds. Three distinct areas of endemism are defined by distributions of Oahu Mecyclothorax: the Waianae Range, the north Koolau Range and the south Koolau Range. Species distributions in two other carabid beetle genera in Hawaii containing native species-Blackburnia Sharp and Bembidion Latreille-congruently define these areas. The historical range of sampling dates is compared for Mecyclothorax species across the three areas, with the greatest diminution of recently collected species-level diversity characterizing the south Koolau Range, where several Mecyclothorax species are characterized both by restricted geographic distributions within the developmental footprint of Honolulu, and by a lack of recent field collections, suggesting that they may qualify for endangered species status.