Reassembling a lost lowland carabid beetle assemblage (Coleoptera) from Kauai, Hawaiian Islands

A late Holocene but prehistoric carabid beetle fauna from the lowland Makauwahi Cave, Kauai, is characterised. Seven extinct species – Blackburnia burneyi, B. cryptipes, B. godzilla, B. menehune, B. mothra, B. ovata and B. rugosa, spp. nov. (tribe Platynini) – represent the first Hawaiian insect species to be newly described from subfossil specimens. Four extant Blackburnia spp. – B. aterrima (Sharp), B. bryophila Liebherr, B. pavida (Sharp), and B. posticata (Sharp) – and three extant species of tribe Bembidiini – Bembidion ignicola Blackburn, B. pacificum Sharp and Tachys oahuensis Blackburn – are also represented. All subfossil fragments are disarticulated, with physical dimensions and cladistic analysis used to associate the major somites – head, prothorax and elytra – for description of the new species. The seven new Makauwahi Cave species support recognition of a lowland area of endemism adjoining Haupu, a low-stature 700 m elevation ridgeline in southern Kauai. Four of the extinct Blackburnia are adelphotaxa to extant species currently found at higher elevations in Kauai. Addition of these lowland specialists to the phylogenetic hypothesis undercuts applicability of the taxon cycle for interpreting evolutionary history of these taxa. Two of the extinct species are Kauai representatives in clades that subsequently colonised younger Hawaiian Islands, enhancing support for the progressive biogeographic colonisation of the archipelago by this lineage. And three of the extinct Blackburnia species comprised larger beetles than those of any extant Kauai Blackburnia, consistent with the evolution of island gigantism in the lowland habitats of Kauai.

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

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.