The Mecyclothorax beetles (Coleoptera, Carabidae, Moriomorphini) of Tahiti, Society Islands

Abstract

The 101 species of Mecyclothorax Sharp known to inhabit Tahiti Island, French Polynesia are taxonomically revised, including 28 species that are newly described: Mecyclothorax claridgeiae sp. n., Mecyclothorax jeanyvesi sp. n., Mecyclothorax poria sp. n., Mecyclothorax aano sp. n., Mecyclothorax papau sp. n., Mecyclothorax manina sp. n., Mecyclothorax everardi sp. n., Mecyclothorax ramagei sp. n., Mecyclothorax pitohitiensis sp. n., Mecyclothorax curtisi sp. n., Mecyclothorax hoeahiti sp. n., Mecyclothorax ninamu sp. n., Mecyclothorax kokone sp. n., Mecyclothorax paahonu sp. n., Mecyclothorax kayballae sp. n., Mecyclothorax ehu sp. n., Mecyclothorax papuhiti sp. n., Mecyclothorax tuea sp. n., Mecyclothorax taatitore sp. n., Mecyclothorax konemata sp. n., Mecyclothorax arboricola sp. n., Mecyclothorax rahimata sp. n., M. oaoa sp. n., Mecyclothorax maninapopoti sp. n., Mecyclothorax hunapopoti sp. n., Mecyclothorax fefemata sp. n., Mecyclothorax maninamata sp. n., and Mecyclothorax niho sp. n. Mecyclothorax muriauxioides Perrault, 1984 is newly synonymized with Mecyclothorax muriauxi Perrault, 1978. Lectotypes are designated for: Thriscothorax altiusculus Britton, 1938; Thriscothorax bryobius Britton, 1938; Mecyclothorax globosus Britton, 1948: and Mecyclothorax sabulicola Britton, 1948. Dichotomous identification keys augmented by dorsal habitus and male aedeagal photographs are provided to the various species-groups and all included species. The spermatophore of Mecyclothorax papau sp. n. is described, with the ampulla and collar found to correspond dimensionally to the length of the internal sac flagellar plate. Variation among characters of the female reproductive tract is presented for all newly described plus other representative species comprising the radiation. Taxa are assigned to species groups, modified from the classification of G.G. Perrault, based on derived character states polarized using the Australian outgroup taxon Mecyclothorax punctipennis (MacLeay). Much of the species-level diversity on this small Pacific island is partitioned allopatrically over very small distributional ranges. No species is shared between Tahiti Nui and Tahiti Iti, and nearly all species in Tahiti Nui are geographically restricted to one ridgelike massif of that volcano. Cladistically similar species are often distributed on different massifs suggesting that vicariance associated with erosional valley formation has facilitated speciation, however several instances in which sister species occupy sympatric distributions on the same ridge system demonstrate that speciation may also occur across extremely localized landscapes. Such localized differentiation is facilitated by the low vagility of these small-bodied, flightless predators whose fragmented populations can persist and diverge within spatially limited habitat patches. The intense philopatry of Tahitian Mecyclothorax spp. coupled with the highly dissected landscape has produced the geographically densest adaptive radiation on Earth. This radiation has occurred very ra...

Cladistic classification of Mecyclothorax Sharp (Coleoptera, Carabidae, Moriomorphini) and taxonomic revision of the New Caledonian subgenus Phacothorax Jeannel

“…Examination of illustrations of male genitalia for other New Guinean species (Baehr 1992(Baehr , 1995(Baehr , 1998(Baehr , 2002(Baehr , 2008(Baehr , 2014 indicates that the entire 22 species currently known from New Guinea belong to this subgenus. Phylogenetic placement of M. montivagus of Hawaii, and M. marau of Tahiti near M. punctipennis of Australia, the hypothesized colonist taxon for both the Hawaiian and Tahitian radiations (Liebherr 2013(Liebherr , 2015 indicates that these species appropriately act as surrogates for the entire 239 species of the Hawaiian Mecyclothorax radiation (Liebherr 2015) plus the 108 species comprising the Society Island radiation on Tahiti and Moorea (Liebherr 2012(Liebherr , 2013. The Australian Mecyclothorax fauna is shown to be biogeographically polyphyletic, with the Australian species M. lateralis, M. minutus, M. ambiguus, and M. punctipennis latecomers (Fig.…”

“…The number of dorsal elytral setae associated with the third elytral interval is indicated using Arabic numbers. The positions of these setae are illustrated in Liebherr (2013: fig. 2) and Liebherr (2015: fig.…”

“…Mecyclothorax punctipennis was also the source taxon for the propagule that colonized St. Paul and Amsterdam Islands, resulting in the very similar but distinct species M. sculptopunctatus. Liebherr (2013) proposed that M. punctipennis is also the species that produced a propagule that colonized Tahiti in the Society Islands, with M. striatopunctatus Perrault as the most generalized taxon in that radiation. Individuals of M. striatopunctatus were not available for this analysis, being returned to the Paris Museum when all types were deposited (Liebherr 2013), and so the less generalized M. marau was used as a surrogate.…”

“…Liebherr (2013) proposed that M. punctipennis is also the species that produced a propagule that colonized Tahiti in the Society Islands, with M. striatopunctatus Perrault as the most generalized taxon in that radiation. Individuals of M. striatopunctatus were not available for this analysis, being returned to the Paris Museum when all types were deposited (Liebherr 2013), and so the less generalized M. marau was used as a surrogate. This substitution results in the French Polynesian representative species being placed as adelphotaxon to the five species associated with M. ambiguus and M. punctipennis.…”

“…Only phylogenetic analysis of Cyphocoleus plus a broad array of potential outgroups allowed such a hypothesis to be proposed. Conversely, immense disparity across an island radiation may evolve adaptively in isolated and restricted island situations over a very short time, such as with Mecyclothorax carabid beetles of the Society and Hawaiian Islands (Liebherr 2013(Liebherr , 2015. Characterizing such biological diversity is the first step toward hypothesizing the context within which a particular lineage has evolved.…”