Mecyclothorax cordithorax Liebherr

Liebherr, James K., 2015, The Mecyclothorax beetles (Coleoptera, Carabidae, Moriomorphini) of Haleakala-, Maui: Keystone of a hyperdiverse Hawaiian radiation, ZooKeys 544, pp. 1-407 : 169-171

Taxon classification Animalia Coleoptera Carabidae

(069) Mecyclothorax cordithorax Liebherr Figs 83E, 84E, 87D, 88 C–I, 89

Mecyclothorax cordithorax Liebherr 2005b: 115.

Mecyclothorax robustus Sharp, Loope et al. 1988: 55, Cole et al. 1992: 1317 (misidentifications).

Diagnosis.

This, the most commonly encountered Mecyclothorax species on Haleakalā, can be diagnosed by the distinctly punctate elytral striae (Fig. 87D), little upraised sutural interval, and transverse pronotum with constricted base, MPW/PL = 1.25-1.38, MPW/BPW = 1.46-1.56. In body proportions this species approaches the Mecyclothorax planipennis - Mecyclothorax planatus species pair, but the cuticular microsculpture of Mecyclothorax cordithorax beetles is much smoother and more transverse, with the pronotal disc, for example, covered with a mixture of shallow transverse mesh and shallow transverse lines. Setal formula 2 2 2 2. Standardized body length 4.4-6.2 mm (vast majority of beetles> 4.6 mm length).

Identification

(n = 5). The eyes are moderately convex, ocular ratio = 1.40-1.48. The pronotal disc is smooth with shallow transverse wrinkles-looking like lap marks on a painted surface-with the distinctly depressed median base covered with isolated puncture and more rugose, longitudinal wrinkles. The elytral striation is well developed, with striae 1-4 continuous and deep to the elytral apex. Striae 5-6 are shallower laterally and apically, with 6 interrupted between some punctures, and stria 7 traceable only as a series of shallow, isolated elongate punctures. Stria 7 is deep on the elytral apex, with interval 8 medially convex laterad the deep stria. The microsculpture on the vertex comprises isodiametric sculpticells in transverse rows. The pronotal median base is covered with distinct isodiametric sculpticells resulting in a granulate surface. The elytral disc has upraised isodiametric sculpticells mixed with transversely stretched sculpticells, the resultant mesh with a reflective surface. The body is rufous to rufobrunneous with a variable piceous cast, contrasting with the flavous legs.

Male genitalia (n = 7). Aedeagal median lobe robust, distance from parameral articulation to tip 3.2 × depth at midlength (Fig. 88 D–E, G, I); apex little extended beyond ostial opening, flattened apically, tip acutely rounded (Fig. 88G, I) to acutely pointed (Fig. 88 D–E); median lobe slightly curved rightward near apex in ventral view, left margin converging toward right to bluntly rounded tip (Fig. 88F, H); internal sac with small dorsal ostial microtrichial patch and larger, heavily spiculated and projected ventral ostial microtrichial patch (Fig. 88I); flagellar plate large, length 0.61 × parameral articulation-tip distance.

Female reproductive tract (n = 3). Bursa copulatrix columnar, apically narrowed, length 0.97-1.03 mm, breadth 0.40-0.45 mm (Fig. 83E); bursal walls moderately opaque, thickly wrinkled; gonocoxite 1 with 4 apical fringe setae, 6-9 smaller setae on medial surface (Fig. 84E); gonocoxite 2 broad basally, subtriangular with angled apex, tip tightly rounded, 2 stout lateral ensiform setae, apical nematiform setae on medial surface at 0.75 × gonocoxite length.

Holotype.

Female (CUIC) designated by Liebherr (2005b: 116). Type locality is HI: Maui, Haleakalā, Haleakalā N.P., Hosmer’s Grove, 2060 m el.

Distribution and habitat.

Of all of the open country, high-elevation species, Mecyclothorax cordithorax has a very broad distribution that is unique among Haleakalā Mecyclothorax (Fig. 89). It occupies shrubland habitats from 1600-2750 m elevation, but does not occur at Haleakalā summit. It occurs in Haleakalā Crater, but only where there is some topographic relief, such as along the margins at Paliku, Kaupō Gap, or Holua, or mid-crater at Pu‘u Māmane. Its native microhabitats include Deschampsia nubigena (hairgrass) tufts, leaf litter under Sophora chrysophylla ( māmane), koa and ‘ōhi‘a trunks in mesic forest, as well as microhabitats associated with various other native plants: Cheirodendron ('ōlapa), Coprosma (pilo), Dryopteris ferns, Leptecophylla (pūkiawe), Pipturus ( māmaki), Rubus ( ‘ākala), and Vaccinium ('ōhelo). It will occupy microhabitats on or near exotic species such as Eucalyptus or Pinus ponderosa . This exceedingly broad occurrence in shrubland habitats begs the question why neither Blackburn nor Perkins collected this species before Sharp’s (1903) revision of the Hawaiian Carabidae . The first specimen was collected by Perkins at 5000 ft. (1524 m) in 1913. Thereafter it was collected by a long line of Hawaiian entomologists and botanists; e.g. Giffard, Timberlake, Forbes, Swezey, Beardsley, Burkhart, Medeiros, Howarth, Stone, Kaholoa‘a, and Krushelnycky. The sudden appearance of this species leading to its status as the dominant shrubland carabid species speaks to an ecological resetting of this community during the early 20th Century.