Trechus namtsoensis, Schmidt, 2009

Schmidt, Joachim, 2009, Taxonomic and biogeographical review of the genus Trechus Clairville, 1806, from the Tibetan Himalaya and the southern central Tibetan Plateau (Coleoptera: Carabidae: Trechini) 2178, Zootaxa 2178 (1), pp. 1-72 : 18-19

Trechus namtsoensis sp. n.

( Figs. 4 , 18, 22 )

Type material: Holotype male, with label data “ TIBET ( South Central ) S Namtso 4730–5000 m, lake shore and Langma Vall., 12–13.VII.07”, “ 30°14’19,6N 90°51’10,7E to ca. 30°37’39N 90°51’56E ” ( SMNS) . Paratypes: 50 males, 27 females, with same label data as holotype ( BMNH, CGITZ, CKAB, CSCHM, CWR, MNHN, SMNS) ; 3 males, 3 females, S Namtso, Langma Valley , 5100–5150 m, 30°37’39,1N 90°51’56,5E, 13.VII.07 ( CSCHM) ; 1 male, 1 female, E-Tibet, 75 km E of Nakchu , 5000 m, 4.VII.1997, leg. A. Wrzecionko, with additional determinational label “ Trechus pseudocameroni Th. Deuve det. 1997” ( CSCHM) .

Description: Body length: 3.5–4.1 mm.

Colour: Dorsal surface dark brown, moderately shiny. Antennal joints 1–2, palpi, legs, elytral lateral margin and suture light brown. Anterior elytral quarter diffuse bordered lighter brown than posterior parts.

Microsculpture: Discs of head and pronotum smooth, with very faintly engraved almost isodiametric meshes (x100). Surface of elytra with moderately engraved transverse meshes in both sexes (x50).

Head: Average sized, with eyes relatively large and moderately protruding. Temples approximately 1/3 times of length of eyes and strongly wrinkled to the neck. Frontal furrows deep, flattened at level of hind suborbital seta. Antennae moderately long, four antennomeres extend beyond the pronotal base. Antennomere III distinctly longer than antennomeres II and IV, both the latter are alike in length.

Pronotum: Broad and transverse, with sides moderately contracted towards base; proportions WP/LP = 1.38–1.48, WP/WPB = 1.32–1.42, WP/WH = 1.18–1.23, WE/WP = 1.57–1.63. Surface strongly convex, sides evenly rounded and slightly concave bent just anterad of posterior setae. Hind angles small but almost rectangular or slightly obtuse. Marginal gutter narrow, scarcely widened toward base. Basal groove smooth.

Elytra: Oval, broadest almost at mid-length; proportion: WE/LE = 1.30–1.44. Surface convex, not flattened on disc. Shoulders distinct but rounded. Striae impunctate, inner two striae deeply impressed overall, outer striae finer, not deepened before apex, striae VII–VIII usually disappeared. Intervals I–IV slightly convex. The preapical seta is located on the prolonged second stria near to the apex at the beginning of the posterior elytral tenth part.

Male genitalia: Aedeagal median lobe more slender, LE/LA = 2.34–2.52, evenly curved basally and remarkably elongated towards apex, with terminal lamella slightly curved upwards, seen laterally. Basal bulb average in size with velum large. Apex of longer copulatory piece slightly bent upwards before tip, the latter shortly bent downwards. Parameres slender, each with 5 (seldom the right one with 4) setae at tip (same as in Fig. 17 ).

Etymology: The specific epithet refers to the largest lake on central Tibetan Plateau, the Namtso, which extends below the north slope of Nyainqentanglha Shan, on which the new species occurs (adjective).

Identification: Within the fauna of central Tibetan Plateau north of Nyainqentanglha Shan Massif this species is easily to recognize by its aedeagal median lobe with remarkably elongated terminal lamella and by the longer copulatory piece extending needle like toward ostium. It is very similar to the allopatric T. dongulaensis sp. n. from the westernmost Nyainqentanglha Shan Massif, both in external and genital morphological characters, but differs by having two basal antennal segments lightened, pronotal hind angles sharper, aedeagal median lobe more evenly curved on basal half, seen laterally, median lobe terminal lamella longer, and by having the apex of the longer copulatory piece not clubbed. It is also very similar to the allopatric T. thibetanus Jeannel, 1928 , from the Tibetan Himalaya , but differs in the same genital morphological characters as mentioned for differentiation with T. dongulaensis sp. n., and in addition, it differs by having the longer copulatory piece almost straight toward apex and not bilobate at tip, seen laterally.

Relationships: Based on the robust and shortened tip of the longer copulatory piece, T. namtsoensis sp. n. together with T. boulbeni Deuve, 1997 , T. dongulaensis sp. n. and T. thibetanus Jeannel, 1928 forms a terminal group of Tibetan species within the T. thibetanus group.

Distribution and geographical variation: Fig. 98 . Eastern parts of the central Tibetan Plateau north of Nyainqentanglha Shan Massif.

Habitat: Lower alpine zone; vertical distribution approximately 4700–5100 m.

Figures

FIGURE 98. Map of central parts of Tibet and the Himalaya showing distribution of species of the Trechus thibetanus group (white circles), of the Trechus pumoensis group (white squares), of the Trechus rolwalingense group (black circles), and of the Trechus stratiotes group (black squares). 1, T. namtsoensis sp. n. 2, T. dongulaensis sp. n. 3, T. thibetanus Jeannel, 1928. 4, T. glabratus sp. n. 5, T. thorongiensis Schmidt, 1994. 6, T. eutrechoides eutrechoides Deuve, 1992. 7, T. eutrechoides mondaensis Deuve, 1997. 8, T. pumoensis Deuve, 1997. 9, T. tilitshoensis Schmidt, 1994. 10, T. franzianus Mateu & Deuve, 1979. 11, T. muguensis sp. n. 12, T. eremita sp. n. 13, T. aedeagalis sp. n. 14, T. sculptipennis sp. n. 15, T. rolwalingense rolwalingense ssp. n. 16, T. rolwalingense daldunglana ssp. n. 17, T. stratiotes stratiotes ssp. n. 18, T. stratiotes malikasthana ssp. n.

FIGURES 2–11. Pronotum. Fig. 2, Trechus thibetanus Jeannel, 1928, Lectotype. Fig. 3, T. dongulaensis sp. n., paratype, male. Fig. 4, T. namtsoensis sp. n., paratype, male. Fig. 5, T. eutrechoides eutrechoides Deuve, 1992, non-type male specimen from Lamna La. Fig. 6, T. glabratus sp. n., paratype, male. Fig. 7, T. korae sp. n., paratype, male. Fig. 8, T. yak yak ssp. n., paratype, male. Fig. 9, T. yak shogulaensis ssp. n., paratype, male. Fig. 10, T. rolwalingensis rolwalingensis ssp. n., paratype, male. Fig. 11, T. rolwalingensis daldunglana ssp. n., paratype, male.

FIGURES 12–27. Aedeagal median lobe with sclerotized portions of internal sac in lateral view (Figs. 12–18, 23–26; Figs. 14, 17, 23, 26 in addition with parameres) and in dorsal view (Fig. 27); apical portion of the longer copulatory piece (Figs. 19–22). Fig. 12, Trechus thorongiensis Schmidt, 1994, paratype, the arrow pointed to the prolongated basal portion of the shorter copulatory piece. Fig. 13, T. eutrechoides eutrechoides Deuve, 1992, non-type specimen from Rongshar Valley. Fig. 14, T. eutrechoides mondaensis Deuve, 1997, paratype. Figs. 15, 19, T. thibetanus Jeannel, 1928, holotype. Figs. 16, 20, T. thibetanus Jeannel, 1928, non-type specimen from Kampa La. Figs. 17, 21, T. dongulaensis sp. n., paratype. Figs. 18, 22, T. namtsoensis sp. n., paratype. Fig. 23, T. glabratus sp. n., paratype. Fig. 24, T. wrzecionkoi Deuve, 1996, non-type specimen from Gyama, Chungenpo Chong side valley. Fig. 25, T. korae sp. n., paratype. Figs. 26, 27, T. martinae sp. n., paratype.