Temnothorax crasecundus, Seifert, Bernhard & Csoesz, Sandor, 2015

Seifert, Bernhard & Csoesz, Sandor, 2015, Temnothoraxcrasecundus sp. n. - a cryptic Eurocaucasian ant species (Hymenoptera, Formicidae) discovered by Nest Centroid Clustering, ZooKeys 479, pp. 37-64 : 52-55

Taxon classification Animalia Hymenoptera Formicidae

Temnothorax crasecundus sp. n.

Etymology.

In the provisional internal naming system of the senior author the new species had been designated over the years as " Temnothorax crassispinus sp. 2". The taxonomic name, composed of “cra” (first syllable of crassispinus) and “secundus” (= the second), intends to indicate both this history and the close relationship.

Type material.

See above under “Material”.

Description of the worker caste.

All morphometric data given in the following verbal description are arithmetic means of 256 worker individuals calculated by fusing Seifert’s and Csösz’s data sets. Harmonization of the different data sets has been performed by the function CW = 1.0791 * CWb.

Worker (Tables 2, 3; Figs 12-14; compare with photos of Temnothorax crassispinus type in Figs 15-17): Medium-sized species (CS 641 µm, ML 760 µm). Head weakly elongated but significantly more than in Temnothorax crassispinus (CL/CW 1.069 vs. 1.055, CL/CWb 1.153 vs. 1.139). Head in dorsal aspect with strongly convex postocular sides, convex genae and straight posterior margin. Eyes with a moderate distance from posterior margin of vertex (PoOc/CL 0.391) and medium-sized in terms of the genus but significantly smaller than in Temnothorax crassipinus (EYE/CS 0.210 vs. 0.216). Scape moderately long (SL/CS 0.762, SL/CSb 0.793) and with variable pubescence: with the scape directed caudad, pubescence is appressed to decumbent (0-15°) at inner margin and more subdecumbent (30°) at outer margin. Frontal carinae rather distant (FRS/CS 0.361), their median part more or less parallel. Sculpture on central vertex regularly longitudinally carinulate. A transversal line between the frontal carinae, positioned immediately posterior of the frontal triangle, crosses 21-23 carinulae. A small longitudinal zone on median vertex occasionally without sculpture and shining. Lateral vertex and head with a more irregular sculpture, being a mixture of microreticulate and rugulose structures. Antennal sockets on shining ground surrounded by 7-8 concentric rugulae. Clypeus between sagittal level of frontal carinae rather smooth but with 5-8 longitudinal carinulae. Frontal triangle with very delicate microsculpture and 0-4 longitudinal carinulae.

Mesosoma moderately wide (MW/CS 0.608) and metanotal depression always developed (MpGr/CS 2.1%). Propodeal spines rather long and acute but distinctly shorter than in Temnothorax crassipinus (SPST/CS 0.283 vs. 0.322). Distance of their bases and tips rather large but significantly smaller than in Temnothorax crassipinus (SPBA/CS 0.286 vs. 0.300, SPTI/CS 0.324 vs. 0.353), spine tips slightly curving inwards. Direction of spines in lateral view deviating from longitudinal axis of mesosoma by 26-29°. Mesosoma irregularly microreticulate-rugulose with few superimposed longitudinal rugae on promesonotum. Metapleuron more regularly longitudinally carinate-rugose.

Petiole in lateral view rather high and with a weakly concave frontal face; the anterior profiles of node and peduncle form an angle of about 150-155° whereas anterior and dorsal profiles of node form an angle of 90-105°. Dorsal profile of node weakly convex or nearly straight and moderately long, steeply sloping down to caudal cylinder. The profiles of this slope and of the caudal cylinder form an angle of about 140°. Whole surface of petiolar and postpetiolar nodes microreticulate with a mesh width of 9-13 µm. Two longitudinal rugae typically demarcate the margin of dorsal petiolar plane while the sides of petiolar tergites are stabilized by one longitudinal carina/ruga on each side.

Overall body color dirty yellow to light brown with a strong yellowish component. Mesosoma, appendages, waist and basis of first gaster tergite usually lighter yellow to dirty yellow. Head dorsum and the posterior surfaces of gaster tergites usually darker, generally yellowish brown. Lighter heads occur.

A more simple means for species delimitation.

There is considerable overlap in each of the 29 shape characters and absolute size (Tables 2 and 3) and a much larger one on individual level (data not shown). This excludes a simple separation of Temnothorax crasecundus sp. n. and Temnothorax crassispinus by single characters. The complex species delimitation procedures presented above require much training of the investigator and a high-quality optical equipment. Even then, data recording for a single nest sample composed of three workers needs 100-120 minutes. In order to allow a practitioner of biodiversity or ecosystem research a more easy approach to the problem, we developed a more simplified determination rule using six absolute measurements. With all measurements given in mm, the discriminant

D(6) = 22.058*PoOc+17.640*SL-66.166*SPST+38.233*MW-28.926*PPW -35.873*SPTI-1.797

classified 203 nest samples with an error of 3.4%. Samples with an arithmetic mean of D(6) <0 are determined as Temnothorax crassispinus and those with larger values as Temnothorax crasecundus sp. n. With PoOc, SL and SPST being recorded bilaterally, a trained investigator needs for the resulting nine measurements about 15 minutes per individual.

The most simple means for separation of Temnothorax crasecundus from Temnothorax nylanderi is geography: the shortest distance between a site of both species is 1000 km and a closing of this broad gap is prevented by habitat saturation of the omnipresent, highly competitive Temnothorax crassipinus . A rather simple phenotypical species delimitation is possible using three absolute measurements. With all measurements given in mm, the discriminant

D(3) = 129.53* SPBA– 120.88*PPW+133.8*MpGR +4.446

classified 87 nest samples with an error of 3.4%. Samples with an arithmetic mean of D(3) <0.64 are determined as Temnothorax nylanderi and those with larger values as Temnothorax crasecundus sp. n.

Zoogeography and biology.

The present zoogeography (Fig. 11) suggests that Temnothorax crasecundus sp. n. survived the last glaciation in an Aegean / West Anatolian arboreal refuge centre near to sea level. The refuge of Temnothorax crassispinus should have been situated rather close to that area in the lowlands of the West Balkans along the eastern Adria and was divided from the Temnothorax crasecundus sp. n. refuge by the Dinaric and Greek mountains. Unhindered by its competing sibling species, there was probably a fast postglacial spreading of Temnothorax crasecundus sp. n. to the north and northeast over Bulgaria, Romania, Moldova and the southern Ukraine to Caucasia and to the east over Asia Minor to Transcaucasia. Spreading to the west was blocked by a front-line confrontation with Temnothorax crassispinus - the underlying mechanisms stabilizing this parapatry are probably comparable to those along the Central European front line between Temnothorax nylanderi and Temnothorax crassispinus ( Pusch et al. 2006). Postglacial spreading of Temnothorax crassispinus was rapid in northern and northeastern direction. The southern limit of its distribution in the Ukraine and south Russia coincides with the southern border of the natural range of the woodland steppe ( Bohn et al. 2000). Despite a larger distance of its Pleistocene refuge from wintercold continental areas of European Russia, Temnothorax crassispinus obviously arrived here before Temnothorax crasecundus . This colonization advantage is probably explained by a higher freezing resistance: the most wintercold known site in Temnothorax crassipinus near Kazan / Russia has a mean January temperature of -13 °C and that of Temnothorax crasecundus near Erzurum / East Anatolia one of -10.5 °C (climatic data from www.weather-and-climate.com). Biology and ecology of Temnothorax crasecundus sp. n. are not studied in detail. Nests were found on ground of deciduous or coniferous forests in microspaces such as hollow acorns, nuts, rotten twigs or galls. Nest populations are monogynous.