Lasius obscuratus Stitz 1930

Seifert, Bernhard, 2020, A taxonomic revision of the Palaearctic members of the subgenus Lasius s. str. (Hymenoptera, Formicidae), Soil Organisms 92 (1), pp. 15-86 : 55

4.4.12 Lasius obscuratus Stitz 1930

Lasius brunneus var. obscuratus Stitz 1930 [type investigation]

Type material: Lectotype worker labelled “West- Pamir VII.X. 28 leg. Reinig ”, ”Dschailgan 7 x. 1800m “. ” LECTOTYPE designated by E.O.Wilson 1954“, “ Lasius brunneus obscurata Stitz lectotype ”, “Type”, “GBIF -D/FoCol 2739 specimen and label data documented”; 3 paralectotype workers labelled “West-Pamir VII.X. 28 leg. Reinig ”, ”Dschailgan 7 x. 1800 m “ “ Lasius brunneus Latr. obscurata St.”; depository ZM Berlin.

Lasius gebaueri Seifert 1992 syn. nov.

[type investigation]

Lasius gebaueri Seifert 1992

Type material: Holotype and 5 paratype workers on the same pin labelled ”Qinhai: Xining 101.53 E, 36.34 N 18.7.1990 leg. Gebauer Trocken Canon“; 3 paratype workers on the same pin labelled ”Quinghai Chaka 99.16 E, 36.49 N 13.6.1990 Wermutsteppe“; depository SMN Görlitz.

All material examined. A total of 58 nest samples with 167 workers were subject to NUMOBAT investigation. These originated from Armenia (1 sample), Georgia (13), China (12), Iran (3), Mongolia (21), Russia (3), Tadzhikistan (1) and Turkey (4). For details see supplementary information S1.

Geographic range. Huge range in Asia between 27°E to 115°E and 34.5°N to 53.2°N. Known from entire Asia Minor, Great Caucasus, Armenia, N Iran (Elburs Mountains ), Tadzhikistan, Mongolia and NE Tibet. The altitudinal distribution ranges from 900 to 2600 m in Asia Minor and Great Caucasus , from 1900 to 3160 in Elburs Mountains and W Pamirs, from 1300 to 3400 m in NE Tibet and Gansu, from 700 to 2100 m in Mongolia, and from 536 to 620 m near Lake Baikal.

Diagnosis ( Tab. 3 , Figs. 23 –24; key; images in www. antWeb.org with specimen identifiers ANTWEB1008435, FOCOL0749, FOCOL2738, FOCOL 2739):

Absolute size rather small (CS 840 µm). Scape and head length indices and number of mandibular dents medium (SL/CS 900 0.956, CL/CW 900 1.065, MaDe 900 8.4). Clypeal pubescence moderately dense (sqPDCL 900 4.35). Pronotal setae of medium length (PnHL/CS 900 0.140), significantly longer than gular setae (GuHL/CS 900 0.091). Dorsum of scape and extensor profile of hind tibia without or only very few semierect setae. It differs from the sister species L. psammophilus by longer terminal segment of maxillary palps (MP6/CS 900 0.173 vs. 0.145). Coloration: head, mesosoma and gaster dark brown, mandibles, antennae, and legs light yellowish-brown.

Biology. It prefers habitats with xerothermous conditions such as open steppe habitats with diverse phytoassociations, short-grassy pastures and light steppe forest. It was also found in less dry habitats such as cut meadows, floodplain pastures, sunny willow stands or montane stunted- growth forest at the tree line. Nest were found in soil, preferentially under stones.

Comments. The morphology of L. obscuratus shows a significant structuring in dependence from geography. 69 specimens fromtheBaikalregion, Mongolia and northeast Tibet ( L. gebaueri in my conception of 1992) differ from 63 specimens of the remaining western population ( L. obscuratus in my former conception) by shorter pronotal setae (PnHL/CS 900 0.134 vs. 0.152), larger eyes (EYE/ CS 900 0.248 vs. 0.240) and smaller postocular distance (PoOc/CL 900 0.229 vs. 0.239). All these differences are significant for p <0.0001 if tested in a one-tailed ANOVA. A LDA considering all 16 standard characters classified 97.0% of 132 individuals in agreement with geography whereas only 90.2% were confirmed by a LOOCV-LDA. Furthermore, a two-step cluster analysis classified 93.2% of the individuals in agreement with geography. These data appear problematic. The final decision to synonymize L. gebaueri with L. obscuratus is based on the very incongruent results of different forms of NC-clustering: NC-part.kmeans could only recognize a single cluster whereas NC-part.hclust distinguished three clusters with a geographic distribution hardly to believe. NC-Ward presented two clusters but grouped two Mongolian-Tibetan samples together with samples from Asia Minor and three samples from Asia Minor together with Mongolian-Tibetan samples – this means 10.2% disagreement with the geographic hypothesis in 49 evaluated nest samples. NC-NMDS-k.means also showed 10.2% disagreement to expectations from geography.

Figures

Figs. 23 and 24: Lasius obscuratus