Mecyclothorax (Mecyclothorax) spiculatus subsp. subgenus, Mecyclothorax Sharp, 1903

Liebherr, James K., 2018, Cladistic classification of Mecyclothorax Sharp (Coleoptera, Carabidae, Moriomorphini) and taxonomic revision of the New Caledonian subgenus Phacothorax Jeannel, Deutsche Entomologische Zeitschrift 65 (1), pp. 1-63 : 13

subgenus Mecyclothorax Sharp, 1903

Diagnosis.

This subgenus holds most of the species-level diversity in the genus, and within those radiations character diversity is rampant, making setal configurations, body form, or mensural characters useless for diagnosis. The best means to diagnose this group is through male genitalic characters, as no species of this subgenus studied to date exhibit a flagellum on the internal sac. Instead, the gonopore is surrounded by either a donut-shaped, soft expansion, or this area of the sac bears a scoop-like flagellar plate, well sclerotized and even ridged, with the gonopore present in membrane lying on the convex surface of this plate (Fig. 4F, G ). The male median lobe also exhibits an opercular flap: i.e. a sclerotized triangle articulated with membrane that lies at the distal end of the ostium (Fig. 4G ). Male parameres are elongate, with the left paramere generally narrow basally with the apex extended as an attenuate whip (Fig. 5D ). External characters differ greatly across the pectinate comb of taxa comprising the base of the radiation - M. monteithi to M. globicollis (Fig. 7 ) - though several external characters can assist in assignment of species to this subgenus. First, the labrum is emarginate apically, either distinctly as in M. goweri (Fig. 1A ), or less so as in M. montivagus (Fig. 8D ). The ligular margin is generally truncate with the ligular setae well separated (Fig. 1G ), though as exceptions, the ligula is apically rounded in the Papuan taxa M. brispex and M. andersoni (Fig. 7 , Liebherr 2017b). The prosternum exhibits a smooth to distinctly punctate anteapical groove, though never any other punctures. The parascutellar striole is present, and may be smooth or punctate, with up to 8 punctures along its length (Fig. 8D-E ). The female reproductive tract is nearly exclusively characterized by the spermathecal duct entering the dorsal surface of the bursa directly dorsad the juncture of the common oviduct with the bursa copulatrix (Fig. 6F ). However, based on the cladistic analysis (Fig. 7 ), entry of the spermathecal duct at the bursal-common oviduct juncture-as in subgenera Eucyclothorax and Qecyclothorax -atavistically and independently re-evolves in M. brispex and the Australian sister taxa M. lateralis and M. minutus (Fig. 6E ).

Member species.

The immense diversity of species comprising this subgenus is represented by 25 species in the cladistic analysis. The various species known from Norfolk Island ( Moore 1985), Lord Howe Island ( Moore 1992), Borneo ( Baehr and Lorenz 1999), Java ( Andrewes 1933, Louwerens 1949, 1953; 3 of 5 resident species analyzed); Papua New Guinea (8 species, Guéorguiev 2013, Liebherr 2008a, 2017b), St. Paul and Amsterdam Islands ( Enderlein 1909, Jeannel 1940), and New Zealand ( Liebherr and Marris 2009) all are members of this clade (Fig. 7 ). Examination of illustrations of male genitalia for other New Guinean species ( Baehr 1992, 1995, 1998, 2002, 2008, 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, 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, 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. 7 ) relative to member taxa of Eucyclothorax and Qecyclothorax , with the late-arriving branch of the Australian Mecyclothorax fauna having been derived from New Guinean roots. The two species recently described from Timor Leste ( Baehr and Reid 2017) also appear to be members of this subgenus based on their gracile body form with cordate pronotum, largely impunctate ventral body surface, and lack of a flagellum in the male aedeagal median lobe.

Figures

Figure 1. Head and mouthpart structures of Mecyclothorax spp. A-C. Head capsule, dorsal view: A, M. goweri; B, M. fleutiauxi; C, M. laterorectus. D-I, Mentum, labial palps and ligula: D, M. peryphoides, ventral view; E, M. storeyi, ventral view; F, M. amplipennis, dorsal view; G, M. montivagus, dorsal view; H, M. kanak, ventral view; I, M. fleutiauxi, ventral view. Abbreviations include: aso, anterior supraorbital seta; pso, posterior supraorbital seta.

Figure 4. Male aedeagal median lobe and parameres of Mecyclothorax spp., right lateral view, internal sac everted in C-G: A, M. blackburni; B-C, M. peryphoides; D, M. moorei; E, M. lewisensis; F, M. punctipennis; G, M. montivagus. See Table 2 for abbreviations.

Figure 5. Paired left (above) and right (below) parameres of Mecyclothorax spp. (ectal view): A, M. blackburni; B, M. storeyi; C, M. amplipennis; D, M. montivagus; E, M. laterobustus. As the aedeagal assembly of M. storeyi males is inverted relative to other Mecyclothorax species (Moore 1984), the configuration of the upper, or right paramere of M. storeyi should be compared to the ventral, or left parameres of the other species, and vice versa.

Figure 6. Female reproductive tract, gonocoxites and associated laterotergites, Amblytelus and Mecyclothorax spp: A, A. matthewsi; B, A. brevis; C, M. blackburni; D, M. storeyi; E, M. minutus; F, M. rectangulus. See Table 2 for abbreviations.

Figure 7. Strict consensus cladogram of 16 equally most-parsimonious trees derived from cladistic analysis of 65 moriomorphine taxa, including the secondary outgroup Neonomius laevicollis, six primary outgroup taxa in Amblytelus and allied genera, and 58 ingroup terminals; 57 Mecyclothorax species plus two genitalic forms of M. andersoni. Species terminals are labeled with species name and three-letter abbreviation of relevant generic or subgeneric name. Full listing of included taxa along with subgeneric assignments is presented in Table 2. Cladistic analysis is based on 137 characters (see character descriptions for nature of each character Areas occupied by the included taxa indicated by abbreviations following species epithets: Bo, Borneo; EOZ, eastern Australia, i. e. east of the Nullarbor Plain; FP, French Polynesia, Tahiti; HI, Hawaiian Islands, Maui; Jv, Java; LH, Lord Howe Island; NC, New Caledonia; Nf, Norfolk Island; NNZ, North Island of New Zealand; NZ, generally distributed across New Zealand; OZ, generally distributed across Australia; PNG, Papua New Guinea; QOZ, restricted to Queensland, Australia; SNZ, South Island of New Zealand plus Chatham Islands; SP & A, St. Paul and Amsterdam Islands; WOZ, western Australia, i. e. west of the Nullarbor Plain.

Figure 8. Mecyclothorax spp., dorsal view, with subgeneric assignments: A, M. (Eucyclothorax, subgen. n.) Mecyclothorax blackburni (type species); B, M. (Qecyclothorax, subgen. n.) Mecyclothorax storeyi (type species); C, M. (Meonochilus, status n.) Meonochilus amplipennis (type species); D, M. (Mecyclothorax) montivagus (type species); E, M. (Mecyclothorax) lissus.