Mecyclothorax pau, Liebherr, James K., 2015

Liebherr, James K., 2015, The Mecyclothorax beetles (Coleoptera, Carabidae, Moriomorphini) of Haleakala-, Maui: Keystone of a hyperdiverse Hawaiian radiation, ZooKeys 544, pp. 1-407 : 292-297

Taxon classification Animalia Coleoptera Carabidae

(116) Mecyclothorax pau sp. n. Figs 154E, 155E, 158E, 161 E–K, 162, 163

Diagnosis.

This (Fig. 158E), the third and last species of the Mecyclothorax palustroides -based triad to be taxonomically treated, is diagnosed by the following combination: 1, lateral elytral intervals as dark or only gradually paler laterally than the disc, a condi tion shared with Mecyclothorax tauberorum (Fig. 158 C–D); 2, pronotal median base distinctly punctate, with ~19 punctures each side, the punctures along the juncture of disc and median base elongate, a condition shared with Mecyclothorax palustroides (Fig. 149B); and 3, elytral microsculpture a shallow transverse mesh, sculpticells a mixture of isodiametric in transverse rows and transverse, breadth 2 × length, with adjacent sculpticells tiled, their surfaces flat, and thus the surface slightly glossy. Setal formula 2 1 2 0. Standardized body length 4.0-5.3 mm.

Description

(n = 5). [The above description of Mecyclothorax palustroides can serve to describe this species. All diagnostic characters are presented above, so only the various recorded ratios are presented below.] Eyes moderately convex, ocular ratio = 1.51-1.58, ocular lobe ratio = 0.7.8-0.86. Pronotum slightly transverse, MPW/PL = 1.16-1.21, variably constricted basally, MPW/BPW = 1.59-1.69; pronotal apical width subequal to greater than basal width, APW/BPW = 0.99-1.13. Elytra subovoid, MEW/HuW = 2.19-2.39.

Male genitalia (n = 43). Aedeagal median lobe variably robust, distance from parameral articulation to tip 4.4 –4.1× depth at midlength (Fig. 161E, I); apex extended 1.6 –2.5× depth beyond ostial opening, the extension narrow to moderately broad (Fig. 161E, H); median lobe shaft straight in ventral view, apex offset to right side with left (dorsal) margin convex (Fig. 161G) and tip bluntly rounded; internal sac variable, either a long curved cylinder (Figs 161H, 162 A–D) or bilobed with a smaller basal lobe and larger apical lobe (Fig. 161I), the sac surface covered with microspicules only; flagellar plate moderately large, length 0.40 × parameral articulation-tip distance in the individual with bilobed sac (Fig. 161I), or large, length 0.54 –0.61× parameral articulation-tip distance in the balance of everted individuals with cylindrical sac (Figs 161H, 162). As the sac length can be assessed in uneverted specimens based on the plate’s shadow in backlit photographs (e.g. 161E, F, J–L), it is concluded that only one dissected male (Fig. 161I) has the bilobed sac condition with the associated small flagellar plate. The individual with the bilobed sac (Fig. 161I; lot 19980511.01, CUIC) was one of two males collected at State Camp on Helele‘ike‘oha Stream. A second male collected at that site (Fig. 161J; lot 19980512.11, NMNH) exhibits the long flagellar plate condition (i.e. plate length 0.55 × parameral articulation-tip distance, Fig. 161J), Cylindrical-sac, large-plate males are also observed to the north of State Camp at Poouli Cabin (Fig. 161F, H), and to east and south in Hāna Bogs and Kīpahulu Valley (Figs 161K, 162 A–B), and on the Manawainui Planeze (Figs 161L, 162 C–D). Because both the cylindrical and bilobed conditions are observed sympatrically at State Camp, they are interpreted as two forms of an infraspecific polymorphism. Various hypotheses for the origin of this polymorphism might include: 1, the bilobed male condition is based on a rare allele primitively shared with the sympatrically distributed Mecyclothorax bilobatus (Fig. 150E, F); or 2, the bilobed male condition is the product of recent hybridization between the sympatric Mecyclothorax pau and Mecyclothorax bilobatus .

Female reproductive tract (n = 1). Bursa copulatrix vase shaped, parallel sided with basal constriction just distad vagina, overall length 1.05 mm, midlength breadth 0.43 mm, basal constriction 0.25 mm broad (Fig. 154E): bursal walls translucent, thickly wrinkled; gonocoxite 1 with 4 apical fringe setae, a curved seta at medioapical angle and 9-10 smaller setae on medial surface (Fig. 155E); gonocoxite 2 falcate with acuminate apex, the lateral margin slightly expanded near apex, thick basal extension curved at terminus, 2 elongate lateral ensiform setae, apical nematiform setae on medioventral surface at 0.71 × gonocoxite length.

Holotype.

Male (BPBM) dissected and labeled: Wai Anapanapa / 6600' // Maui, T.H. / VIII-45 // R.L. Mitchell / Coll. // H. St. John / Collector // HOLOTYPE / Mecyclothorax / pau / Liebherr / det. / J.K. Liebherr 2015 (black-margined red label).

Paratypes.

278 specimens (see Appendix).

Etymology.

The epithet pau given to this terminal species in the revision is the useful and definitive Hawaiian word for: finished, ended, completed, over, all done, final ( Pukui et al. 1975). Given the intense endemism of Haleakalā Mecyclothorax species, there is no doubt that this epithet will be superseded in the future by names of presently undescribed species.

Distribution and habitat.

Mecyclothorax pau is known from an isolated population on the western margin of Ke‘anae Valley (1325 m elevation), and a main massing of populations from Kuhiwa Valley through the Hāna Bogs, Kīpahulu Valley, and the Manawainui Planeze (Fig. 163). The eastern populations occupy habitats 915-2045 m elevation. Nearly all specimens have been collected in association with mossy ‘ōhi‘a, either from trunks or horizontal logs, or by sifting humus and litter from around trees. In a small fraction of collecting events, Cibotium ( hāpu‘u) tree ferns were living on ‘ōhi‘a nurse logs. The beetles may be beaten from ferns at night.