Taxonomic review of Australian Mecyclothorax Sharp (Coleoptera, Carabidae, Moriomorphini) with special emphasis on the M. lophoides (Chaudoir) species complex

Abstract

The Australian fauna of Mecyclothorax Sharp (Coleoptera: Carabidae: Moriomorphini) is reviewed, with special focus on species assigned to the monophyletic subgenus Eucyclothorax Liebherr: M. isolatus, sp. n. from Western Australia, M. moorei Baehr, M. punctatus (Sloane), M. curtus (Sloane), M. blackburni (Sloane); M. eyrensis (Blackburn); M. peryphoides (Blackburn); M. darlingtoni, sp. n. from Queensland; M. jameswalkeri, sp. n. from Western Australia; M. lophoides (Chaudoir); and M. cordicollis (Sloane). The last six species listed above–the M. lophoides species complex–have been the source of long-term confusion for taxonomists, with male genitalic characters providing trouble-free species circumscription. One new subspecies, M. lewisensis estriatus, subsp. n. from Queensland is added to the seven previously described taxa of the monophyletic subgenus Qecyclothorax Liebherr. The balance of the fauna consists of four species in the subgenus Mecyclothorax: 1 and 2, the sister-species pair M. lateralis (Castelnau) and M. minutus (Castelnau); 3, M. ambiguus (Erichson); and 4, M. punctipennis (MacLeay). Mecyclothorax fortis (Blackburn), syn. n., is newly synonymized with M. minutus. Mecyclothorax ovalis Sloane is recombined as Neonomius ovalis (Sloane), comb. n., and a neotype is designated to replace the destroyed holotype. Phylogenetic relationships for the Australian Mecyclothorax are proposed based on information from 68 terminal taxa and 139 morphological characters. The biogeographic history of Australian Mecyclothorax is deduced based the sister-group relationship between Mecyclothorax and the Amblytelus-related genera, with both groups hypothesized to have originated during the late Eocene. Diversification within Mecyclothorax has occurred since then in montane rainforests of tropical Queensland, temperate forest biomes of the southwest and southeast, and in grasslands and riparian habitats adjacent and inland from those forests. Several species presently occupy interior desert regions, though no sister species mutually occupy such climatically harsh habitats. The M. lophoides species complex exhibits profound male genitalic diversification within the context of conserved external anatomy. This disparity is investigated with regard to the functional interaction of the male internal sac flagellum and female spermathecal duct. Though limited association of flagellar and spermathecal duct configurations can be documented, several factors complicate proposing a general evolutionary mechanism for the observed data. These include: 1, the occurrence of derived, elongate spermathecal ducts in three species, two of which exhibit very long male flagella, whereas males of the third exhibit a very short flagellum; and 2, a highly derived and exaggerated male flagellar configuration shared across a sister-species pair even though the two species can be robustly diagnosed using external anatomical characters, other significant genitalic differences involving male parameral setation, and biogeographic allopatry associated with differential occupation of desert versus forest biomes.