Taxonomic review of Australian Mecyclothorax Sharp (Coleoptera, Carabidae, Moriomorphini) with special emphasis on the M. lophoides (Chaudoir) species complex
Authors: Liebherr James K. 
Published: August 2018

The Australian fauna ofMecyclothoraxSharp (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.mooreiBaehr,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); andM.cordicollis(Sloane). The last six species listed above–theM.lophoidesspecies complex–have been the source of long-term confusion for taxonomists, with male genitalic characters providing trouble-free species circumscription. One new subspecies,M.lewisensisestriatus,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:1and2, the sister-species pairM.lateralis(Castelnau) andM.minutus(Castelnau);3,M.ambiguus(Erichson); and4,M.punctipennis(MacLeay).Mecyclothoraxfortis(Blackburn),syn. n., is newly synonymized withM.minutus.MecyclothoraxovalisSloane is recombined asNeonomiusovalis(Sloane),comb. n., and a neotype is designated to replace the destroyed holotype. Phylogenetic relationships for the AustralianMecyclothoraxare proposed based on information from 68 terminal taxa and 139 morphological characters. The biogeographic history of AustralianMecyclothoraxis deduced based the sister-group relationship betweenMecyclothoraxand theAmblytelus-related genera, with both groups hypothesized to have originated during the late Eocene. Diversification withinMecyclothoraxhas 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. TheM.lophoidesspecies 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; and2, 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.