Geostiba (Sibiota) tigrani, Assing, 2017

Assing, Volker, 2017, On the Geostiba fauna of Armenia (Coleoptera: Staphylinidae: Aleocharinae), Linzer biologische Beiträge 49 (2), pp. 1075-1092 : 1082-1086

Geostiba (Sibiota) tigrani nov.sp. (Figs 22-38, Map 3 )

T y p e m a t e r i a l: Holotype 3: " ARMENIA [10] – Sevani range E Sevan lake , 40°23'51''N, 45°29'53''E, 2025 m, oak forest, 28. VI.2017, V. Assing / Holotypus 3 Geostiba tigrani sp. n. det. V. Assing 2017 " (cAss) . Paratypes: 1333, 23 ♀♀: same data as holotype (cAss, MNB) ; 1133, 2 ♀♀: same data as holotype, but leg. Schülke (MNB) ; 1133, 14 ♀♀: " ARMENIA [11] – SSE Dilijan, Semyonovka, 40°40'09''N, 44°52'35''E, 2050 m, Sorbus forest , 29. VI.2017, V. Assing" (cAss, MNB) ; 433, 3♀♀: same data, but leg. Schülke (MNB) ; 633, 3 ♀♀: " ARMENIA [12] – SSE Dilijan , Semyonovka, 40°40'12''N, 44°53'05''E, 1900 m, stream valley, 29.VI.2017, V. Assing" (cAss); 1♀: same data, but leg. Schülke (MNB); 13, 2♀♀: " ARMENIA [17] – E Dilijan, road Ttujur-Berd 40°44'04''N, 45°18'10''E, 1930 m, trees & bushes, 30.VI.2017, V. Assing " (cAss); 533, 4 ♀♀: " ARMENIA [28] – WSW Dilijan, Kalavan, 40°37'52''N, 45°05'46''E, 1960 m, forest, sifted, 5.VII.2017, V. Assing" (cAss, MNB) ; 333, 3♀♀: same data, but leg. Schülke (MNB) ; 433, 11 ♀♀: " ARMENIA [29] – WSW Dilijan, Kalavan, 40°37'45''N, 45°05'31''E, 2100 m, forest, sifted, 5.VII.2017, V. Assing" (cAss, MNB) ; 1♀: same data, but leg. Schülke (MNB) .

E t y m o l o g y: This species is dedicated to Tigran Ghrejyan, PhD student at the Zoological Institute in Yerevan, an excellent and entertaining field guide in summer 2017. His expertise and guidance significantly contributed to the collecting results of this field trip.

D e s c r i p t i o n: Body length 1.9-2.7 mm; length of forebody 0.8-1.2 mm. Coloration: body dark-yellowish to reddish-brown, with the head and the preapical abdominal segments often slightly darker. Eyes small, larger than antennomere III in cross-section, with pigmentation, and composed of approximately 6-10 ommatidia. Pronotum with or without a shallow longitudinal impression on either side of midline. Hind wings completely reduced.

3: elytra (Fig. 22) with pronounced, narrow, anteriorly slightly broader carina extending along whole suture, disc with usually extensive and more or less pronounced impression, punctation very fine, non-granulose; abdominal tergite VII (Fig. 23) with a pair of pronounced, rather broad, smooth, and strongly elevated carinae posteriorly; posterior margin of tergite VIII variably shaped, broadly convex to obtusely pointed in the middle; sternite VIII broadly convex; median lobe of aedeagus (Figs 24-30) 0.24-0.25 mm long, without distinct semi-transparent spines in internal sac; ventral process weakly curved in lateral view; paramere not distinctive.

♀: elytra and abdominal tergite VII without modifications; tergite VIII shaped as in male; posterior margin of sternite VIII convex, in the middle usually very shallowly concave; spermathecal capsule (Figs 31-38) with undilated distal portion and moderately long proximal portion.

I n t r a s p e c i f i c v a r i a t i o n: The male secondary sexual characters may be reduced to various degrees in small males. In males at the very low end of the size variation, the pair of carinae on tergite VII is completely obsolete and the elytral carinae are very weakly pronounced. Remarkably, tergite VII of one male from Semyonovka has a single tubercle instead of a pair of carinae. The aedeagus of this specimen (Fig. 28), however, is identical to those of other males of G. tigrani , suggesting that they are conspecific. This conclusion is supported by an examination of the spermathecae of syntopic females, which are identical to those of G. tigrani from the type locality. This is yet another example of the variability of the modifications of the male tergite VII in Armenian Sibiota species (see also the comment in the section on G. pambakica ).

C o m p a r a t i v e n o t e s: Onlytwo Sibiota species with a pair of carinae on the male tergite VII were previously known from Armenia, G. pambakica ASSING, 2016 from North Armenia and G. meghruica ASSING, 2016 from South Armenia. The new species is distinguished from both by darker average coloration and the shape of the spermatheca, from G. pambakica additionally by larger eyes with more ommatidia ( G. pambakica : eyes smaller and composed of approximately five ommatidia), larger average size, less sharp sutural carinae on the male elytra, more pronounced carinae on the male tergite VII, and a slightly larger aedeagus, and from G. meghruica by more pronounced sutural carinae and a slightly smaller aedeagus. For illustrations of G. pambakica and G. meghruica see Figs 1-13 and ASSING (2016).

Figs 22-38: Geostiba tigrani from the type locality (22-26, 31-33), Semyonovka (27-28, 34-35; 28: male with median tubercle on tergite VII), E Dilijan (29, 36), and Kalavan (30, 37-38): (22) male elytra; (23) male tergite VII; (24-30) median lobe of aedeagus in lateral and in ventral view; (31- 38) spermatheca. Scale bars: 22-23: 0.2 mm; 24-38: 0.1 mm.

D i s t r i b u t i o n a n d n a t u r a l h i s t o r y: The currently known records suggest that G. tigrani is distributed in the mountain ranges to the north and northwest of Sevan lake ( Map 3 ). The specimens were sifted from litter and roots in forests or forest margins with dominant oak, whitebeam, hornbeam, beech, and/or birch at altitudes of 1900-2100 m. In one locality to the east of Dilijan (sample locality 17), the species was collected together with S. unituber .

Figures

Map 3: Distribution of Sibiota species in Armenia: G. pambakica (white circles); G. tigrani (black circles); G. unicuneata (white diamonds), G. immutata (black star), G. meghruica (white triangles); G. sp. 1 (black triangle); G. sp. 2 (white star).

Figs 1-13: Geostiba pambakica from road Berd – Ijevan (1-2, 9-10) and from pass road E Ijevan (3-8, 11-13; 8: male with single median tubercle on tergite VII): (1-8) median lobe of aedeagus in lateral and in ventral view; (9-13) spermatheca. Scale bars: 0.1 mm.