Trachelus stipa, Budak & Blank & Başibüyük, 2017

Budak, Mahir, Blank, Stephan M. & Başibüyük, Hasan H., 2017, Trachelus stipa (Hymenoptera: Cephidae), a new stem sawfly from Central Anatolia associated with feather grass (Stipa holosericea, Poaceae), Zootaxa 4277 (1), pp. 99-110 : 101-104

Trachelus stipa , sp. nov.

Description. Female. Color ( Fig. 2 C–D). Head and thorax black, tegula completely black or medially yellow, basis of mandible mostly blackish yellow. Legs predominantly red yellow, coxae, trochanters, bases of tibiae black, distal tarsomeres infuscated (particularly on hind leg). Wings strongly infuscate grey, venation black, pterostigma dark brown, anterior edge pale ( Fig. 3 A). Abdomen predominantly red yellow, tergum 1 black, tergum 2 predominantly dark brown to black, tergum 3 with some brown spots, tergum 7 posteriorly with brown spots or with transverse, medially more or less interrupted black band, tergum 8 posteriorly with transverse, medially narrowed black band, sterna 2–3 predominantly black, subsequent sterna with large, posterior-medial black spot decreasing in size towards distal segments. Ovipositor sheath black, distal edge of valvifer 2 pale brown, ventral and distal edge of valvula 3 brown. Cercus black with yellow basis.

Species Sex Localities GenBank accession numbers

COI Cyt b EF-1α Structure. Length 11.5–14.0 mm. Distance between antennal toruli 0.8 × as wide as distance between antennal torulus and tentorial pit. Antenna with 20–22 flagellomeres, flagellomere 11 quadrate, preapical flagellomeres 1.6–1.7 × as wide as long and 1.4 × as wide as flagellomere 1. POL: OOL: OCL = 1.0: 0.8–0.9: 2.3. Metatibia 0.8 × as long as metatarsus, frequently with 1 subapical spur (6 out of 10 females), longer apical spur 1.8 × as long as apical width of metatibia. Metatarsomere 1 0.9 × as long as combined length of metatarsomeres 2–4. Claw of hind leg with stout subapical tooth, deep notch between basis of claw and subapical tooth, and strongly curved outer side ( Fig. 4 A). Vein 2r-rs of forewing short, ca 200 µm ( Fig. 3 A). Ovipositor sheath in lateral view 2.2–2.3 mm long, about as long as metatibia, valvula 3 0.3 × as long as valvifer 2, valvifer 2 ventrally weakly convex, dorsal edge of valvula 3 basally straight and distally concave, ventral edge of valvula 3 convex, sloping dorsally towards narrowly raised tip ( Fig. 5 A). Combined width of valvulae 3 in dorsal view 7.5 × as wide as maximum width of cercus, ovipositor sheath protruding to level of tip of cercus. Lateral edges of valvulae 3 weakly converging towards tip ( Fig. 5 A). Head largely smooth, subantennal area with scattered, fine pits (diameter <10 µm), vertex with scattered, larger pits (up to 20 µm in diameter), pronotum shallowly pitted, mesoscutum deeply pitted (20–30 µm), mesoscutellum largely smooth, medial terga and particularly sterna densely pitted (up to 40 µm).

Male. Length ca 11.0 mm ( Fig. 2 A–B). Colour of head, legs and wings similar as in female, tegula often black (6 out of 10). Abdomen black or with yellow lateral spots distally on terga 4–6, very small yellow lateral spots distally on terga 7–8, more or less distinct dorso-medial brown spots on tergum 4–6(–8), tergum 9 completely yellow.

Surface structure similar as in female. Hind leg with one or two preapical spurs (6 specimens with one and 4 with two). Claw of hind leg with subapical tooth shorter and narrower than apical tooth, without deep notch between basis of claw and subapical tooth, outer side of claw almost straight in basal half. Sterna 7–8 with shallow depressions densely covered with erected, dark brown setae, setaceous fields covering most of sterna except for a 100–150 µm wide zone along distal and latero-distal edge ( Figs 5 C–D). Distal edge of sternum 9 deeply notched ( Fig. 6 A).

Type material. Holotype ♀: Turkey, Sivas province, Sivas, campus of Cumhuriyet University , 39.702° N 37.030° E, ca. 1300 m altitude, 17.vi.2007 ( ECCUS). Paratypes: 1♂, same site, 26.v.2010 ; 1♂ same site, 30.v.2010; 2♀, same site, 12.vi.2010; 8♀ 7♂, same site, 12.vi.2011; 2♂ same site, 13.vi.2013 (all ECCUS, SDEI); 1♂, Konya province, Sille , ca. 37.933°N 32.433°E, ca. 1200 m altitude, 08.vi.1978, leg. M. Schwarz ( SDEI).

Host plant. At least 3 females were observed to oviposit into stalks of Stipa holosericea Trin. & Rupr. (Poaceae) .

Etymology. The species name, a noun in apposition, has been chosen in accordance with the genus name of the grass which was oviposited in Sivas.

Molecular analysis. The complete dataset of COI, cyt b, and EF-1α nucleotide sequences for five Trachelus and two outgroup species of Cephini consisted of 1,742 positions (736 bp of COI, 433 bp of cyt b and 573 bp of EF-1α). Male and female specimens of the new species have identical nucleotide sequences for each investigated gene region. The pairwise genetic distance of the new species to other investigated Trachelus species is ranging from 2.1–2.3 % for the nuclear gene EF-1α and 11.3–12.5 % and 11.3–14.8 % for the mitochondrial genes COI and cyt b, respectively. Interspecific pairwise differences within the Trachelus species ranged from 11.3–14.1 % for COI, 11.3–18.2 % for cyt b, and 1.2–3.0 % for EF-1α ( Tables 2–3). The BI and NJ trees for the concatenated data set is presented in Figure 1. In the BI tree (Fig. 1A), the basal position of T. iudaicus within Trachelus is strongly supported by a high posterior probability (PP) of 0.99. In this tree, T. stipa splits off comparatively basally, after T. iudaicus , but this branching has gained only low support (PP = 0.67) as well as the position of T. troglodyta (PP = 0.58). The remaining species constitute a clade with T. tabidus and T. libanensis representing the most recent speciation event (PP = 0.93). In the NJ tree (Fig. 1B), T. iudaicus and T. tabidus are included in a common clade which forms the sister group of the other Trachelus species. T. stipa and T. troglodyta constitute sister taxa with a considerable genetic distance between them ( Table 2–3), and T. libanensis is the sister taxon of this clade. The most basal branching is corroborated by a bootstrap value of 0.75, but the bootstrap values for the internal branching pattern of Trachelus are low (0.35–0.45).

Figures

FIGURE 2. Trachelus stipa: A. ♂, lateral view; B. ♂, dorsal view; C. ♀, lateral view; D. ♀, dorsal view.

FIGURE 3. Forewings in male and female: A. female, B. male Trachelus stipa; C. female, D. male T. troglodyta; E. female, F. male T. iudaicus; G. female, H. male T. libanensis; I. female, J. male T. tabidus.

FIGURE 4. Claw of hind leg in female: A. Trachelus stipa; B. T. troglodyta; C. T. iudaicus; D. T libanensis; E. T. tabidus.

FIGURE 5. Posterior part of abdomen in Trachelus stipa: A. ♀, lateral view; B. ♀, dorsal view; C. ♂, lateral view; D. ♂, dorsal view.

FIGURE 6. Hypopygium of male: A. Trachelus stipa; B. T. troglodyta; C. T. iudaicus; D. T. libanensis; E. T. tabidus.