Trechus chaklaensis, 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 : 57-58

Trechus chaklaensis sp. n.

( Figs. 71, 72 , 95 )

Type material: Holotype male, with label data “ TIBET South Centr. 17.VII.07, Lhundup area, above Chak La 5000–5200 m, ca. 30°07’05N 91°16’31E ” ( BMNH).

Paratypes: 35 males, 11 females, with same label data as holotype ( BMNH, CKAB, CSCHM, CWR, MNHN, SMNS) .

Description: Body length: 2.9–3.3 mm.

Colour: Dorsal surface brown or light brown, shiny, with head and posterior 2/3 of elytra often cloudy darkened. Palpi, antennal base and legs yellowish brown, antennal segments III–XI often darkened.

Microsculpture: Supraorbital area and discs of pronotum and elytra with very faintly engraved meshes, almost isodiametric on head and more transverse on pronotum and elytra (x100). More deeply engraved meshes in frontal furrows of head and in pronotal basal depression.

Head: Average, with eyes small and slightly protruding; temples approximately 3/4 of length of eyes and strongly wrinkled to the neck. Frontal furrows not or very slightly flattened at level of hind suborbital seta. Antennae moderately short, 2.5 antennomeres extend beyond the pronotal base. Antennomere III slightly longer than antennomeres II and IV, both the latter are alike in length.

Pronotum: Relatively variable in form and proportions: Cordate or subcordate, moderately or more strongly transverse and +/- strongly contracted towards base; WP/LP = 1.25–1.38, WP/WPB = 1.28–1.38, WP/WH = 1.23–1.28, WE/WP = 1.52–1.71. Surface strongly convex. Sides evenly rounded in anterior 2/3 and straight or +/- curtly concave anterad of hind angles; the latter relatively small, +/- obtuse, in some specimens pointed, in some specimens almost rounded. Marginal gutter narrow, slightly widened anterad of laterobasal depressions. Base almost rectilinear, distinctly curved anteriorly at outer fifth; basal depressions smooth or with fine longitudinal wrinkles both sides of pronotal middle.

Elytra: Oval, broadest at mid-length or little behind, with proportion WE/LE = 1.48–1.53. Surface strongly convex, not or slightly flattened on disc. Shoulders rounded, indistinct. Striae faintly punctate, first stria fully deep impressed, second and third striae deeply impressed on disc but reduced at base and extreme apex, fourth stria much shallower, striae V and VI hardly visible and stria VII completely reduced. Stria VIII moderately or slightly impressed from level of the fifth umbilicate pore backwards and more deeply impressed at levels of seventh and eighth pores. Second and third interval strongly convex. Preapical seta is located in the third interval often close to the second stria and at the beginning of the posterior elytral seventh or eighth.

Male genitalia: Aedeagal median lobe short (LE/LA = 3.40–3.47), more strongly curved in basal half, elongate towards apex, with terminal lamella moderately short; the latter almost straight, very slightly bent downwards at tip. Basal bulb average. Internal sac in lateral view with a strongly bent leaf-like copulatory piece in middle of third quarter of median lobe.

Etymology: The specific name is derived from the type locality, the Chak La pass (adjective).

Identification: Within the Tibetan fauna this new species is easily to distinguish by the extraordinary form of the copulatory piece of the male genitalia. Due to the pale body and the more strongly reduced lateral elytral striae in external characters T. chaklaensis sp. n. is similar to T. korae sp. n. of the T. wrzecionkoi group and to T. mieheorum sp. n. of the T. dacatraianus group, but beside the very different form of aedeagal median lobe it differs from both species in having a smaller body size, temples longer and micromeshes on elytral disc more weakly engraved. The new species is also similar to the species of the T. antonini group, especially due to the form and the small size of the aedeagal median lobe but it is easily distinguished by the transverse direction of the internal sac sclerotized portion.

Relationships: Similarities in general habitus and in external shape of the aedeagal median lobe of the new species suggest closer relationships with species of the T. antonini group, however, the latter species group is characterized by having completely different aedeagal internal sac structures: The sclerotized portions always lie in a longitudinal direction, whereas in T. chaklaensis sp. n. the sclerotized portion is transversely folded. Thus, the taxonomic position of T. chaklaensis sp. n. at present remains unclear.

Distribution: Fig. 99 . Transhimalaya approximately 60 km north east of Lhasa: Currently only known from the mountain slopes south east and above the Chak La pass.

Habitat: Higher alpine zone. The specimens were found under stones along a melt water brook at altitudes of 5000–5100 m, and on the top of a mountain crest at altitudes of 5100–5200 m.

Figures

FIGURE 99. Map of Southern Central Tibet showing distribution of species of the Trechus wrzecionkoi group (white circles), of the Trechus dacatraianus group (white squares), of the Trechus solhoeyi group (black circle), and of the Trechus chaklaensis group (black square). 1, T. wrzecionkoi Deuve, 1996. 2, T. martinae sp. n. 3, T. korae sp. n. 4, T. damchungensis Deuve, 1997. 5, T. hodeberti Deuve, 1997. 6, T. bastropi sp. n. 7, T. mieheorum sp. n. 8, T. solhoeyi sp. n. 9, T. chaklaensis sp. n.

FIGURES 65–80. Aedeagal median lobe with sclerotized portions of internal sac in lateral view (Figs. 65–71, 77–80; Figs. 65, 68–71, 79, 80 in addition with parameres) and in dorsal view (Figs. 72–76). Figs. 65, 74, Trechus astrophilus sp. n., paratype. Fig. 66, T. lama sp. n., paratype. Fig. 67, T. singularis sp. n., holotype. Fig. 68, T. tsampa sp. n., paratype. Figs. 69, 76, T. yak yak ssp. n., paratype. Figs. 70, 73, T. religiosus sp. n., paratype. Figs. 71, 72, T. chaklaensis sp. n., paratype. Fig. 75, T. yak shogulaensis ssp. n., paratype. Fig. 77, T. antonini sp. n., non-type specimen from Lhachen La (= locus typicus). Fig. 78, T. folwarcznyi Deuve, 1997, non-type specimen from Shogu La (= locus typicus). Fig. 79, T. rarus sp. n., holotype. Fig. 80, T. tseringi sp. n., paratype.

FIGURES 93–95. Habitus. Trechus lama sp. n., paratype, male (93). T. religiosus sp. n., paratype, male (94). T. chaklaensis sp. n., paratype, female (95).