Aphaenogaster illyrica

Aphaenogaster illyrica is a subterranean species. In Bulgaria, it was mostly collected in beech forests in wet sites, close to streams, while in Slovenia it was found in a large karstic depression situated in a sub-montane karst grassland, party covered with sparse trees and shrubs. The specimens collected in 2003 were found in subterranean pitfall traps set in soil at the depth of 30–50 cm among limestone rocks. The records of A. illyrica well above 1000 m a.s.l. or those from beech forests at lower altitudes indicate that it tolerates lower temperatures, which is relatively rare in other species of the genus.

Identification
The sculpture of head and mesosoma, head shape, scape length, and length of funicular segments place this species into the Aphaenogaster subterranea species group. Aphaenogaster illyrica differs from other members of this group in the combination of the following features: mesonotum clearly raised above the surface of pronotum, long and thin propodeal spines, as long as or longer than 0.7 length of the first segment of funiculus, elongated mesosoma, large body size (ML more than 1.64 mm, HW more than 1.02 mm), anterolateral sides of pronotum regularly convex, without setose angulations or tubercles, and yellowish brown to rusty brown body colour. In most of the other members of the group (i.e., Aphaenogaster lesbica from Lesbos, Aphaenogaster maculifrons from the western Turkey, Aphaenogaster subterranea, pronotum and mesonotum form a regular convexity, without mesonotum raised above the surface of pronotum, propodeal spines are shorter, not longer than half length of the first segment of antennal funiculus, ML is less than 1.60 mm, and HW less than 1.0 mm.

Aphaenogaster illyrica most closely resembles Aphaenogaster graeca from Mount Olympus (see Table 1) in morphometric data and general body shape. The new species differs form A. graeca in having a brighter and more uniform body colouration (yellowish brown to rusty brown vs. dark brown), weaker head sculpture, which fades laterad, less distinctly sculptured pronotum especially at sides, propodeum smooth and lacking longitudinal rugae on almost of whole lateral surface, and absence of long rugae at the base of the first gaster tergite (Figs 9–12).

Stout members of the A. splendida species group, i.e., Aphaenogaster festae and its relatives with the mesonotum raised clearly above the surface of pronotum, clearly differ in the yellowish body, short propodeal spines directed distinctly upwards, and elongate segments 2–4 of antennal funiculus, always 1.5 times or more longer than wide.

We also recognise several yet undescribed members of the A. subterranea group, which will be a subject for further, more advanced studies. Aphaenogaster illyrica is most similar to an undescribed species collected on the island of Cephalonia, especially in its long propodeal spines and mesonotum slightly raised above the surface of pronotum, but the undescribed form differs in having a distinctly microreticulated and dull dorsal and occipital parts of the head surface and dorsum of pronotum, as well as in the anterolateral corners of pronotum bearing setose tubercles.

Distribution
All known records of Aphaenogaster illyrica are restricted to the mountainous areas of the Balkan Peninsula, from the altitudes of 500 m to 1420 m a.s.l. Its range stretches from the Dinaric Alps in southern Slovenia and western Croatia to Osogovo-Belasica Massif in southwestern Bulgaria and the adjacent Kerkini Mts. in Greece and to Golešnica Mt. in North Macedonia. This distribution area is much larger compared to the area of the sister species Aphaenogaster graeca, whose distribution range is limited to the massif of Mount Olympus and adjacent mountain ranges.

Distribution based on Regional Taxon Lists
Palaearctic Region: Bulgaria, Croatia, Greece, North Macedonia, Slovenia.

Biology
Details on the habitat of A. illyrica are available only from the Bulgarian and Slovenian records. In Bulgaria, it was mostly collected in beech forests in wet sites, close to streams, on silicate (Belasitsa and Maleshevska Mts.) and limestone (Slavyanka Mt.) rocks. This differs quite dramatically from the Slovenian site, where the ants were found in a large karstic depression (karstic doline) situated in the sub-montane karst grassland, party covered with sparse trees and shrubs. This area is characterised by harsh winters and relatively wet summers. Due to the strong and almost permanent winds, the upper part of the soil is often dry. The specimens collected in 2003 were found in subterranean pitfall traps set in soil at the depth of 30–50 cm among the limestone rocks in the so-called Superficial Subterranean Habitat (SSH) or “Milieu Souterrain Superficiel” (MSS), as originally described (Juberthie et al. 1980; 1981). SSH is a hypogean environment, generally formed by the fragmentation of the bedrock and accumulation of debris, which contains a wide network of air-filled epikartsic spaces, small voids and fissures (Culver and Pipan 2009; Giachino and Vailati 2010) and represents a transition zone between surface soils and deeper subterranean habitats such as caves (Culver and Pipan 2009). A presence of a rare species Aphaenogaster cardenai was already reported from SSH in the Iberian Peninsula (Ortuño et al. 2014). In 2018, we found few scattered workers at the same site while digging in the stony ground to the depth of approximately 50 cm.

Nomenclature

 *  illyrica. Aphaenogaster illyrica Bračko, Lapeva-Gjonova, Salata, Borowiec & Polak, 2019: 93, figs. 1-8 (w.) SLOVENIA.

Type Material

 * Paratypes: BULGARIA: 5 workers (CASENT0872100-CASENT0872104): Maleshevska Mt., Strumyani distr., Dobri Laki vill., 41.58484N, 22.98138E, 650 m, soil traps, along Lebnitsa river, beech and alder trees, 30.07.-20.08.2002, leg. S. Lazarov, T. Ljubomirov (BFUS); 1 worker (CASENT0872105): Belasitsa Mt., Petrch district, Belasitsa hut, 41.370N, 23.187E, 690 m, beech forest, 28.03.2009, leg. R. Bekchiev (BFUS); 15 workers (CASENT0872106-CASENT0872120): Belasitsa Mt., Petrch district, Kamena vill., 41.360N, 23.074E, 500 m, beech forest, along Kamenishka river, soil traps, June 2009, leg. R. Kostova; 02.05.2013, direct sampling, leg. A. Lapeva-Gjonova (BFUS, DBET); 6 workers (CASENT0872121- CASENT0872126): Slavyanka Mt., Sandanski district, Goleshovo vill., 41.42139N, 23.625N, 1094 m, 16.08.2014, leg. A. Lapeva-Gjonova (BFUS); CROATIA: 9 workers (CASENT0872127-CASENT0872135): Oltari, Mt. Senjsko bilo, 7 km NW of Krasno, 44.84604N, 15.00298E, 02.06.1992, leg. A. Schulz, K. Vock (DBET, PW); GREECE: 3 workers (CASENT0872136-CASENT0872138): [Macedonia] Kerkini Mts., Ano Poroia, 41.28563N, 23.03598E, 28.5.1984, V. Vohralik lgt. (PW, DBET); NORTH MACEDONIA: 4 workers (CASENT0872139-CASENT0872142): Golešnica Mts., 2 km S of Aldinci, 41.80189N, 21.42848E, 9.7.2010, 1420 m, V. Vohralik lgt. (DBET, PW); SLOVENIA: 1 worker (CASENT0872143): Mt. Velika Milanja, MSS, Volovja reber, Ilirska Bistrica, SLO, 45.593N, 14.313E, 1060 m, 23.05.2003, leg. S. Polak (DBET); 2 workers (CASENT0872144-CASENT0872145): Mt. Velika Milanja, MSS, Volovja reber, Ilirska Bistrica, SLO, 45.593N, 14.313E, 1060 m, 05.10.2018, leg. G. Bračko (BFUL).
 * Paratypes: BULGARIA: 5 workers (CASENT0872100-CASENT0872104): Maleshevska Mt., Strumyani distr., Dobri Laki vill., 41.58484N, 22.98138E, 650 m, soil traps, along Lebnitsa river, beech and alder trees, 30.07.-20.08.2002, leg. S. Lazarov, T. Ljubomirov (BFUS); 1 worker (CASENT0872105): Belasitsa Mt., Petrch district, Belasitsa hut, 41.370N, 23.187E, 690 m, beech forest, 28.03.2009, leg. R. Bekchiev (BFUS); 15 workers (CASENT0872106-CASENT0872120): Belasitsa Mt., Petrch district, Kamena vill., 41.360N, 23.074E, 500 m, beech forest, along Kamenishka river, soil traps, June 2009, leg. R. Kostova; 02.05.2013, direct sampling, leg. A. Lapeva-Gjonova (BFUS, DBET); 6 workers (CASENT0872121- CASENT0872126): Slavyanka Mt., Sandanski district, Goleshovo vill., 41.42139N, 23.625N, 1094 m, 16.08.2014, leg. A. Lapeva-Gjonova (BFUS); CROATIA: 9 workers (CASENT0872127-CASENT0872135): Oltari, Mt. Senjsko bilo, 7 km NW of Krasno, 44.84604N, 15.00298E, 02.06.1992, leg. A. Schulz, K. Vock (DBET, PW); GREECE: 3 workers (CASENT0872136-CASENT0872138): [Macedonia] Kerkini Mts., Ano Poroia, 41.28563N, 23.03598E, 28.5.1984, V. Vohralik lgt. (PW, DBET); NORTH MACEDONIA: 4 workers (CASENT0872139-CASENT0872142): Golešnica Mts., 2 km S of Aldinci, 41.80189N, 21.42848E, 9.7.2010, 1420 m, V. Vohralik lgt. (DBET, PW); SLOVENIA: 1 worker (CASENT0872143): Mt. Velika Milanja, MSS, Volovja reber, Ilirska Bistrica, SLO, 45.593N, 14.313E, 1060 m, 23.05.2003, leg. S. Polak (DBET); 2 workers (CASENT0872144-CASENT0872145): Mt. Velika Milanja, MSS, Volovja reber, Ilirska Bistrica, SLO, 45.593N, 14.313E, 1060 m, 05.10.2018, leg. G. Bračko (BFUL).