Lasius piliferus Seifert 1992

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 : 56-57

4.4.14 Lasius piliferus Seifert 1992

Lasius piliferus Seifert 1992 [type investigation]

Type material: Holotype plus 4 paratype workers labelled ” Sierra de Gredos , 1600 m 13.5.91-8, 3 km S Hoyos de Espina “; 10 paratype of 2 other nest samples from the same location with date and sample label ”13.5.91-27“ and ”13.5.91-S“; depository SMN Görlitz.

All material examined. A total of 11 nest samples with 53 workers were subject to NUMOBAT investigation. These originated from France (1 sample) and Spain (10). For details see supplementary information S1.

Geographic range. Iberian species. So far only known from 8 sites in the Sierra de Gredos, Sierra de Quadarrama and NE Pyrenees at elevations between 1250 and 1950 m.

Diagnosis ( Tab. 3 , Figs. 27 –28; key; image in www. antWeb.org with specimen identifiers FOCOL0753): Absolute size small (CS 812 µm). Head length index and number of mandibular dents medium (CL/CW 900 1.061, MaDe 900 8.2). Clypeal pubescence rather dilute (sqPDCL 900 4.63). Pronotal setae of medium length (PnHL/CS 900 0.150), significantly longer than gular setae (GuHL/CS 900 0.114). Dorsum of scape without or only single semierect setae. Extensor profile of hind tibia with very few semierect setae (nHT 900 3.2). It differs from the parapatric sister species L. psammophilus by the shorter scape (SL/CS 900 0.929 vs. 0.960), smaller eye (EYE/CS 900 0.220 vs. 0.238) and slightly larger seta counts. Coloration: not differing from situation in L. psammophilus .

Biology. Main habitats are semidry grasslands (pastures grazed by cattle, horse or sheep or S-facing meadows. However, more mesophilic conditions were not avoided. Nest were found under stones.

Comments. L. piliferus and L. psammophilus show significant differences in a number of characters. In 243 specimens with the full set of standard characters available, this is most clearly expressed in EYE/CS 900 (univariate ANOVA F 1,241 = 205.9, p<0.0001), SL/ CS 900 (F 1,241 = 61.9, p<0.0001) and nSt 900 (F 1,241 = 56.7, p<0.0001). Considering the characters SL/CS 900, EYE/ CS 900, GuHL/CS 900, nGen 900 and nSt 900, nest sample means of both species are fully separated in a plot of the first two factors of a PCA. Using both all 16 standard characters or the five selected ones, NC-Ward clustering misclassified only 1.2% of 83 samples in disagreement with the final species hypothesis. On the other hand, NCpart.kmeans, NC-part.hclust and NMDS-kmeans could not confirm the existence of two clusters both in the full or reduced character set. Problems are mainly caused by the two Pyrenean samples: one L. psammophilus sample from near Seu de Urgell (42.366°N, 1.262°E, 1600 m) and one L. piliferus sample from near La Tour de Carol (42.466°N, 1.89°E, 1500m). Considering 10 Spanish and 11 French samples of these species, these two samples are placed in an intermediate position if run as wild cards in an LDA. This may indicate hybridization in the Pyrenean contact zone of both taxa and reminds to the Pyrenean hybrid zone of the grasshoppers Chorthippus parallelus (Zetterstedt 1821) and C. erythropus Faber 1958 . The zoogeographies and postglacial spreading of these grashoppers ( Hewitt 1993) appear analogous to those of L. psammophilus and L. piliferus respectively. In case of synonymization of both taxa by future authors, the least confusion in literature would arise if priority is given to L. psammophilus or if piliferus is ranked as subspecies of the former.

Figures

Figs. 27 and 28: Lasius piliferus; holotype