Colonisation of the Pacific by Bembidion beetles (Coleoptera : Carabidae), with description of Bembidion tahitiense, sp. nov. from Tahiti, French Polynesia

Abstract

Bembidion (Sloanephila) tahitiense, sp. nov. is described from Mont Mauru, an isolated massif of Tahiti Nui volcano. Based on evidence from seven genes (four nuclear protein-coding, one mitochondrial protein-coding, two nuclear ribosomal), its sister group is the Australian B. jacksoniense Guérin-Méneville, with which it shares a synapomorphic spur on the ostium of the male genitalia. In contrast to B. jacksoniense, B. tahitiense is brachypterous, with rounded humeri, constricted posterior pronotal margins and convex body form. Examination of the seven genes in two species of the Hawaiian subgenus Nesocidium Sharp reveals that the sister group of Nesocidium is subgenus Zecillenus Lindroth from New Zealand. These two subgenera belong to the Ananotaphus complex, a clade inhabiting Australia, New Zealand and Hawaii. The relationships of the second Hawaiian subgenus, Gnatholymnaeum Sharp, are less clear, although Gnatholymnaeum belongs to the Bembidion series (along with Sloanephila and the Ananotaphus complex). Bembidion beetles colonised the Society and Hawaiian islands independently from source areas in the south-west Pacific. Based on parsimonious reconstructions of flight-wing configuration, the Tahitian and Hawaiian colonisations involved winged individuals. Colonisation of the Society and Hawaiian islands by carabid beetles of two other tribes – Platynini and Moriomorphini – follow the dispersal patterns hypothesised for Bembidion.