Lasius vostochni, Seifert, 2020

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 : 63-64

4.4.26 Lasius vostochni sp. nov.

Etymology. Derived from the Russian word восточний, meaning ”eastern“ and referring to the geographic range that is east of the range of the sister species Lasius niger .

Type material. Holotype plus 4 paratype workers on the same pin labelled ”RUS: Ussuri: 42.97N, 133.52E, 160 m; Krivaya-Tal, Flussterrasse, Sandboden L. Kanter 1999.09.07 -43a; 2 paratype workers labelled ”RUS: 51.3528°N, 106.4800°E Gusinoosersk-4W, 604 m Pinus steppe forest under stone I.Antonov 2009.07.11 -145“; depository SMN Görlitz.

All material examined. Only the two type samples with 7 workers were investigated. For details see supplementary information SI1.

Geographic range. Apparently a species with distribution east of the Johannsen line ( De Lattin 1967) with contact to Lasius niger in the South Baikal region.

Diagnosis ( Tab. 6 , Figs. 51 –52; key):

Absolute size rather small (CS 826 µm). Scape length index rather small (SL/CS 900 0.961), maxillary palp length index comparably large (MP6/CS 900 0.192). Eye large (EYE/CS 900 0.252). Number of mandibular dents not recordable in the available material but most probably similar to situation in L. niger . Clypeal pubescence rather dense (sqPDCL 900 3.92). Pronotal setae short (PnHL/ CS 900 0.128). Setae number on dorsum of scape rather low (nSc 900 6.1) but high on extensor profile of hind tibia and metapleuron below propodeal spiracle (nHT 900 14.3, nSt 900 8.0). Coloration: Head, gaster, petiole, coxae, femora and tibiae dark brown; mesosoma sometimes a little lighter; mandibles, scape, trochanter and tibio-femoral joint region pale yellowish-brown.

Biology. Largely unknown. The sample from the southern Sikhote-Alin range was collected on a sandy river terrace within an area of dense woodland and the South Baikal sample in a Pinus steppe forest from under a stone.

Comments. Lasius vostochni sp. nov. differs from its sibling species L. niger by a combination of more numerous metapleural setae, less numerous scape setae, less dense clypeal pubescence and a slightly longer terminal maxillary palp segment. Considering the full set of 16 standard characters in a PCA and calculating nest sample means of the PCA scores, the two samples of L. vostochni sp. nov. are placed separate from 67 samples of L. niger using the first three principal components. Reducing to the six characters CS, MP6/CS 900, dClAn/ CS 900, sqPDCL 900, nSc 900 and nSt 900, L. vostochni sp. nov. is placed separate from L. niger by a PCA on individual level as well as on nest sample level by NC-NMDS.kmeans, NC-Ward and NC-UPGMA clustering. However, conclusions based on such few individuals are problematic. A thorough study of the populations in the Russian Far East should be conducted to confirm the species hypothesis presented here.

Figures

Figs. 51 and 52: Lasius vostochni sp. nov.; holotype