Lasius silvaticus, 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 : 47-48

4.4.1 Lasius brunneus (Latreille 1798)

Formica brunnea Latreille 1798 [conception of Mayr (1861) and neotype fixation] Both the original description and that of Latreille (1802) do not allow a species identification. The locus typicus is Brive/ France. The first unambiguous description was presented by Mayr (1861) that has been adopted by most of the European authors since then. A neotype is fixed herewith in three worker specimens collected near Brive, labelled ”FRA: 44.9125°N, 1.4769°E, Souillac– 1.7 km N, 120 m, tree row, leg. Galkowski 2008.09.07 “ and ” Neotype (top) Lasius brunneus (Latreille 1798) des. Seifert 2019“; depository: SMN Görlitz.

Lasius pallidus (Latreille 1798)

Formica pallida Latreille 1798 [indirect indication] This taxon is not identifiable from data in the original description. Yet, as the synonymization with Lasius brunneus was established by Latreille himself (Latreille 1802), I follow his decision.

Lasius timidus (Foerster 1850)

Formica timida Foerster 1850 [original description] This taxon was described from near Aachen / Germany. The reported morphology (coloration, length of frontal line, pilosity) in combination with zoogeography strongly suggests a synonymy with L. brunneus .

Lasius alienobrunneus Forel 1874

Lasius niger var. alienobrunneus Forel 1874

[type specimens]

Forel did not mention a locus typicus. Five workers stored in MHN Genéve, labelled as ” Typus “ and ”L. alienobrunneus For. / Vaux“ do not show any notable deviation from the normal morphology of L. brunneus both by NUMOBAT data and subjective impression (pictures in www.antweb.org under CASENT0911044).

All material examined. A total of 32 nest samples with 67 workers were subject to NUMOBAT investigation. These originated from Austria (1 sample), Bulgaria (1), England (1), France (3), Germany (11), Greece (1), Italy (1), Spain (2), Sweden (1), Switzerland (2), and Turkey (8). For details see supplementary information SI1.

Geographic range. Eurocaucasian , submeridional and temperate. From S England and Iberia across Central Europe , the Apennine and the Balkans to Asia Minor and the Caucasus. In Scandinavia north to 60°N, absent from Finland. In N Tyrol ascending to 1410 m and in Anatolia at 37°N to 2000 m.

Diagnosis ( Tab. 1 , Figs. 1 –2; images in www.antWeb. org with specimen identifiers CASENT0172717, CASENT0172745, CASENT0172746, CASENT0179886, CASENT0179917, CASENT0179917, CASENT0911044:

The species is rather easily identified by a combination of short scape (SL/CS 900 0.874), broad head (CL/CW 900 1.041), reduced setae numbers on all body parts (nOcc 900 2.0, nGen 900 0.1, nGu 900 1.3, nSC 900 0.0, nHT 900 0.1, nSt 900 1.1) a very smooth pubescence surface on scape and tibiae, and reduced number of mandibular dents (MaDe 900 7.06). The dorsal and posterior profile of propodeum are linear and form a distinct, obtuse angle. The petiole is in anterocaudal view rather rectangular or slightly converging dorsad but typically with straight sides and forming a sharp, weakly emarginate dorsal crest. A typical coloration of medium-sized to large specimens is mesosoma, petiole and appendages light yellowish brown, head a little darker bronze brown and gaster dark to blackish brown. However, small workers from initial colonies may show a homogenously dark coloration as seen in L. lasioides or L. neglectus but can easily be separated by RAV-corrected NUMOBAT data.

Biology. See Seifert (2018).

Comments. For separation from the eastern sister species L. silvaticus sp. nov. and L. himalayanus see there and Tab. 1.

4.4.2 Lasius silvaticus sp. nov.

Etymology. The species name refers to the woodland habitat.

Type material. Holotype plus 2 paratype workers labelled ” IRAN: 36.7198°N, 54.5813°E, Gorgan 19SE, 853 m, Caspian mild and wet, A.B. Yazdi 2016.06.15 -9“ and ” Holotype (bottom) and paratypes Lasius silvaticus Seifert “; 3 paratype workers ” IRAN: 36.7198°N, 54.5813°E, Gorgan 19SE, 853 m, Caspian mild and wet, A.B. Yazdi 2016.06.15 -24“ and ” Paratypes Lasius silvaticus Seifert “; 3 paratype workers ” IRAN: 37.367°N, 55.817°E, Golestan NP, Galesha canyon, 594 m, forest, nest on tree, Paknia 2007.05.23 - 1420“; 3 paratype workers ” IRAN: 37.367°N, 55.817°E, Golestan NP, Galesha canyon, 594 m, forest, nest under stone, Paknia 2007.05.23 - 1427“; all material stored in SMN Görlitz.

All material examined. A total of 9 nest samples with 24 workers from seven localities in the Iran were subject to NUMOBAT investigation. For details see supplementary information SI1.

Geographic range. S Caspian; known so far only from a rather small area between 36.7 and 37.4° N, 54.4 and 55.8°E, and 160 to 900 m a.s.l.

Diagnosis ( Tab. 1 , Figs. 3 –4; key; image in www. antWeb.org with specimen identifier CFH000052): Showing all diagnostic characters of the L. brunneus species complex. The main difference to L. brunneus is the less sparse and longer pilosity on pronotum (PnHL/ CS 900 0.130), underside of head (nGu 900 3.6, GuHL/CS 900 0.125), propodeum and hind tibia (nHT 900 1.6, nSt 900 2.9). Accessory differences are the longer head and smaller postocular distance (CL/CW 900 1.059, PoOc/CS 900 0.235). The coloration is fully comparable to L. brunneus .

Biology. Habitat selection appears to be similar to its sibling species Lasius brunneus : Seven samples were found in wet and humid Caspian broad-leafed forest and one sample in a city park with trees. The nests were both in the wood of trees, under stones, in litter and (in a clearcutting) in soil.

Comments. L. brunneus , L. silvaticus sp. nov. and L. himalayanus are hypothesized here to represent three cryptic species with different geographic distribution. They are clearly clustered on the sample level as different entities by exploratory data analyses using the 16 standard NUMOBAT characters unselectively. The classification error relative to the controlling LDA is 0% in a PCA and a TSCA using the first four principal components. NC-Ward, NC-part.kmeans, NC-part.hclust and NC-NMDS-kmeans misclassify one L. brunneus sample from Aksehir / Turkey as L. himalayanus (=error 2.9% in 34 samples). A mean classification error of 1.9% within six exploratory data analyses is in agreement with the heterospecificity threshold of the GAGE species concept. The three cryptic species seem to be parapatric or allopatric according to the poor information currently available and it will be interesting to see if the current taxonomic assessment would change after investigations in the putative contact zone of L.brunneus and L. silvaticus sp. nov. near the Turkish-Iranian border will have been done. The allopatric data currently available provide a strong signal for species separation: the discriminant D(8) = 40.81*SL–38.9*CW +71.2*PnHL+0.866*nHT– 0.674*sqPDCL+0.246*nSt–2.392 is D(8)= –1.885 ±0.956 [–4.75,0.00] in 56 workers of L. brunneus and D(8) = 4.390 ± 1.098 [2.63, 6.56] in 24 workers of L. silvaticus .

Figures

Figs. 1 and 2: Lasius brunneus; neotype

Figs. 3 and 4: Lasius silvaticus sp. nov.; holotype