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

      Deutsche Entomologische Zeitschrift

      Pensoft Publishers

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          Abstract

          The 15 species of Mecyclothorax Sharp precinctive to New Caledonia are revised and shown by cladistic analysis to comprise a monophyletic lineage, here treated as subgenus Phacothorax Jeannel. The New Caledonian species of subgenus Phacothorax include Mecyclothorax fleutiauxi (Jeannel), M. najtae Deuve, and 13 newly described species: M. jeanneli sp. n., M. laterobustus sp. n., M. laterorectus sp. n., M. laterosinuatus sp. n., M. laterovatulus sp. n., M. manautei sp. n., M. megalovatulus sp. n., M. octavius sp. n., M. paniensis sp. n., M. picdupinsensis sp. n., M. plurisetosus sp. n., and two jointly authored species; M. kanak Moore & Liebherr sp. n., and M. mouensis Moore & Liebherr sp. n.. subgenus Phacothorax is one of five subgenera recognized within genus Mecyclothorax based on cladistic analysis of 65 exemplar taxa utilizing information from 137 morphological characters. The four other monophyletic subgenera include the precinctive Australian Eucyclothorax subgen. n. (type species Mecyclothorax blackburni [Sloane]), the precinctive Queensland Qecyclothorax subgen. n. (type species Mecyclothorax storeyi Moore), the precinctive New Zealand Meonochilus Liebherr & Marris status n., and the geographically widespread and very diverse nominate subgenus, distributed from St. Paul and Amsterdam Islands, eastward across Australia and New Guinea, and in the Sundas, Timor Leste, Lord Howe and Norfolk Islands, New Zealand, and the Society and Hawaiian Islands. The biogeographic history of Mecyclothorax can be derived from the parsimony cladogram time-calibrated by times of origin of particular geographic areas inhabited by resident representative species. Based on sister-group status of subgenus Phacothorax and subgenus Mecyclothorax, and occupation of Lord Howe Island–an island originating no earlier than 6 Ma–by the earliest divergent lineage within subgenus Mecyclothorax, the ancestor of present-day Phacothorax spp. is hypothesized to have colonized New Caledonia 6 Ma, subsequent both to Cretaceous Gondwanan vicariance as well as any Oligocene submergence. Area relationships among the New Caledonian Phacothorax point to earliest diversification incorporating the northern massifs, and most recent diversification on the ultramafic volcanic substrates in the south of Grand Terre. Flight wing loss has played an important role in shaping the various island faunas, both in their morphology as well as their diversity. The retention of flight capability in only a few of the many hundred Mecyclothorax spp. is presented in light of how populations evolve from macropterous colonizing propagules to vestigially winged specialists. Interspecific differences in genitalic structures for the sister-species pair M. fleutiauxi + M. jeanneli are shown to involve functional complementarity of male and female structures. Extensive geographic variation of male genitalia is demonstrated for several New Caledonian Mecyclothorax spp. This variation deviates from the geographically uniform male genitalia exhibited by species in the hyperdiverse Mecyclothorax radiation of Haleakalā volcano, Maui, suggesting that extensive sympatry occurring among species in that diverse species swarm selects for stability within this mate recognition system. Conversely, lower levels of sympatry characterizing the depauperate New Caledonian radiation permit the presence of more extensive male genitalic variation, this variation not selected against due to the lower likelihood of interspecific mating mistakes.

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          Most cited references 45

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              New Caledonia: a very old Darwinian island?

              New Caledonia has generally been considered a continental island, the biota of which largely dates back to Gondwanan times owing to its geological origin and the presence of phylogenetic relicts. This view is contradicted by geological evidence indicating long Palaeocene and Eocene submersions and by recent biogeographic and phylogenetic studies, with molecular or geophysical dating placing the biota no older than the Oligocene. Phylogenetic relicts do not provide conclusive information in this respect, as their presence cannot be explained by simple hypotheses but requires assumption of many ad hoc extinction events. The implication of this new scenario is that all the New Caledonian biota colonized the island since 37 Ma Local richness can be explained by local radiation and adaptation after colonization but also by many dispersal events, often repeated within the same groups of organisms. Local microendemism is another remarkable feature of the biota. It seems to be related to recent speciation mediated by climate, orography, soil type and perhaps unbalanced biotic interactions created by colonization disharmonies. New Caledonia must be considered as a very old Darwinian island, a concept that offers many more fascinating opportunities of study.
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                Author and article information

                Journal
                Deutsche Entomologische Zeitschrift
                DEZ
                Pensoft Publishers
                1860-1324
                1435-1951
                January 18 2018
                January 18 2018
                : 65
                : 1
                : 1-63
                Article
                10.3897/dez.65.21000
                © 2018

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