Survey of the ants (Hymenoptera: Formicidae) of the Greek Thrace

The ant fauna of Greece has been an object of investigations for almost two centuries, but most of the contributions were restricted to particular parts or regions of the country. The first comprehensive checklist, comprising the past studies on Greek ants, was done only recently by Legakis (2011). In the last few years, the ant fauna of Greece was more intensively studied as part of the inventory of the ants of the Mediterranean region (Borowiec and Salata 2012, Borowiec and Salata 2013, Borowiec and Salata 2014b, Borowiec and Salata 2014a, Salata and Borowiec 2015a, Salata and Borowiec 2015b, Salata and Borowiec 2015c). Based on the above mentioned studies, it turned out that the Greek ant fauna is probably the richest in Europe, with about 280 recorded species including almost 20 endemic to this country. Among the geographic regions of Greece, Macedonia has richest ant fauna with at least 158 species recorded, followed by Dodecanese (111), Ionian Islands (107), East Aegean Islands (106), Peloponnese (102), Crete (98), Sterea Ellas (72), Thessaly (67), Cyclades (46), and Epirus (42) respectively (Borowiec & Salata unpublished data). The ants of Greek Thrace have been more or less neglected so far. This region has not been studied in recent years, while older data are very scarce. As a result, only 12 species were mentioned from this region (Legakis 2011). 
 
Greek Thrace (or Western Thrace) is one of the geographic and historical regions of Greece. It is the eastern-most mainland part of the country, bordered by Greek Macedonia to the west, Bulgaria to the north (the southern part of Bulgaria is also known as the Bulgarian or Northern Thrace), Turkish (or Eastern) Thrace to the east and the Aegean Sea to the south. Most of the northern part of Greek Thrace is occupied by the Rhodope Mountains. Larger plains are situated especially in the south-western, central and north-eastern part of the region. A Mediterranean climate prevails in the southern part of Thrace and is modified by continental influences in the Rhodope Mountains (Encyclopaedia Britannica 2015). 
 
To improve the knowledge on Thracian ants, we conducted two field trips, in spring 2014 and in summer 2015, and included some previously collected unpublished material. Altogether, we compiled the samples from more than 70 localities throughout the region. As a result we present a check-list of all ant species recorded so far in Greek Thrace with comments on the taxonomy and distribution of poorly known or unnamed species.


Introduction
The ant fauna of Greece has been an object of investigations for almost two centuries, but most of the contributions were restricted to particular parts or regions of the country. The first comprehensive checklist, comprising the past studies on Greek ants, was done only recently by Legakis (2011). In the last few years, the ant fauna of Greece was more intensively studied as part of the inventory of the ants of the Mediterranean region (Borowiec and Salata 2012, Borowiec and Salata 2013, Borowiec and Salata 2014b, Borowiec and Salata 2014a, Salata and Borowiec 2015a, Salata and Borowiec 2015b, Salata and Borowiec 2015c. Based on the above mentioned studies, it turned out that the Greek ant fauna is probably the richest in Europe, with about 280 recorded species including almost 20 endemic to this country. Among the geographic regions of Greece, Macedonia has richest ant fauna with at least 158 species recorded, followed by Dodecanese (111), Ionian Islands (107), East Aegean Islands (106), Peloponnese (102), Crete (98), Sterea Ellas (72), Thessaly (67), Cyclades (46), and Epirus (42) respectively (Borowiec & Salata unpublished data). The ants of Greek Thrace have been more or less neglected so far. This region has not been studied in recent years, while older data are very scarce. As a result, only 12 species were mentioned from this region (Legakis 2011).
Greek Thrace (or Western Thrace) is one of the geographic and historical regions of Greece. It is the eastern-most mainland part of the country, bordered by Greek Macedonia to the west, Bulgaria to the north (the southern part of Bulgaria is also known as the Bulgarian or Northern Thrace), Turkish (or Eastern) Thrace to the east and the Aegean Sea to the south. Most of the northern part of Greek Thrace is occupied by the Rhodope Mountains. Larger plains are situated especially in the south-western, central and northeastern part of the region. A Mediterranean climate prevails in the southern part of Thrace and is modified by continental influences in the Rhodope Mountains (Encyclopaedia Britannica 2015).
To improve the knowledge on Thracian ants, we conducted two field trips, in spring 2014 and in summer 2015, and included some previously collected unpublished material. Altogether, we compiled the samples from more than 70 localities throughout the region. As a result we present a check-list of all ant species recorded so far in Greek Thrace with comments on the taxonomy and distribution of poorly known or unnamed species.  Images of ant specimens shown in this paper were taken using a Nikon SMZ 1500 and Nikon SMZ 18 stereomicroscopes, Nikon D5200 photo camera and Helicon Focus software. All of them have assigned a CASENT number and are available on www.antweb. org.
Below, we present a list of all known ant species from Greek Thrace with the localities of the sampled material (see Table 1 for the description of locality codes) and literature data.
We give information about the presence of the recorded species in other Greek regions, based on Borowiec and Salata (2012) . We add comments on the taxonomy and distribution of poorly known or unnamed species. Following the list of recorded species, we give notes on the taxa which were mentioned in Legakis (2011), but their occurence in Greek Thrace is doubtful.
Lasius paralienus Seifert, 1992 Records in Greek Thrace: 3, 5, 55 Notes: Leptothorax acervorum was only recorded generally from Greece by Agosti and Collingwood (1987b). In recently collected material we found this species only from two localities in Drama regional unit in Macedonia. Our material from Greece suggests the occurrence of at least three morphospecies of complex in this country but their correct identification will be possible only after the revision of all names proposed in this group.
Plagiolepis pallescens sensu Radchenko (Fig. 7) Records in Greek Thrace: 48,49,67 Distribution in Greece and neighbouring regions: Crete, Cyclades, Dodecanese, East Aegean Is., Epirus, Ionian Is., Macedonia, Peloponnese, Sterea Ellas, Thessaly; Turkish Thrace Notes: Under this taxon we placed the samples of Plagiolepis with densely pubescent first gaster tergite. Radchenko (1996) reviewed members of the genus Plagiolepis from Central and Southern Palaearctic and proposed the name P. pallescens Forel, 1889 for taxon with densely pubescent first gaster tergite of both workers and gynes. We studied syntype of P. pallescens described from Rhodes Island preserved in Museum of Genève (available in AntWeb https://www.antweb.org/specimen/CASENT0909854) which is yellowish and has first gaster tergite sparsely pubescent. We have many samples of yellow coloured and sparsely pubescent mature workers collected from Rhodes and observed nests with workers of exclusively yellow aberration and nests with mixed yellow and brown aberrations. Both light and dark colored specimens showed similar level of sclerotization of cuticle. Thus the light colour in this case is not indicative of callow workers. Our specimens of Plagiolepis pallescens sensu Radchenko have darker colouration, from yellowish brown to brown. Only the callow workers are lighter yellowish. In morphometric characters samples of both yellow and dark aberrations from Rhodes appear to be conspecific with Plagiolepis taurica Santschi, 1920, a sparsely pubescent species which is also variable in colour (Salata and Borowiec in preparation). Plagiolepis schmitzi Forel, 1885 is the only other densely pubescent taxon from the Mediterranean area, distributed from Portugal to Sicily (recent record from Iran by Ghahari et al. 2015 is probably based on misidentification), but it is not conspecific with the eastern form named by Radchenko 1996 as P. pallescens. Therefore, densely pubescent taxon from the eastern part of the Mediterranean Basin has no valid name and its proper identification needs a revision of several available names of infraspecific taxa proposed from the Mediterranean area.  2010) redescribed Solenopsis fugax and suggested that four distinct species groups occur in the territory of Europe and the Mediterranean area. They also suggested that several taxa proposed by Bernard (1950) are probably synonyms but they did not take any formal nomenclatorial decisions. In Thrace, we found samples belonging to at least two distinct morphospecies. One sample from the Rhodope Mountains (no. 1) appears to be true S. fugax. This species seems to be rare in Greece and we have only few samples from Macedonia in our collection. All other samples, characterized by shorter hairs on mesosoma and small gynes, belong to Solenopsis lusitanica group as proposed by Galkowski et al. (2010). Probably most of literature records of S. fugax from lowland, warm areas and regions outside Macedonia and Thrace concern taxa of S. lusitanica group. According to Galkowski et al. 2010, the group comprises three taxa described from the western part of the Mediterranean Basin, but we cannot exclude the presence of other undescribed species in the eastern Mediterranean.

Temnothorax cf. interruptus
Records in Greek Thrace: 9,37,61,64,68 Distribution in Greece and neighbouring regions: Ionian Is., Macedonia, Thessaly; Bulgarian Thrace, Turkish Thrace Notes: Recent studies suggest that true T. interruptus (Schenck, 1852) does not occur in Greece. All Greek populations belong to one or more undescribed taxa of the T. interruptus complex (Csősz et al. in preparation).
Tetramorium cf. semilaeve (Fig. 18) Records in Greek Thrace: 9, 13, 17, 22, 29, 30, 32, 33, 35, 43, 48, 51, 68, 69;Legakis 2011 Distribution in Greece and neighbouring regions: Crete, Cyclades, Dodecanese, East Aegean Is., Epirus, Ionian Is., Macedonia, Peloponnese, Sterea Ellas, Thessaly; Turkish Thrace Notes: Tetramorium semilaeve group from the Balkan Peninsula and Turkish Aegean regions is now under revision (Salata & Borowiec in preparation). We grouped samples with mostly reduced head sculpture under name T. depressum complex (T. hippocratis and at least three unnamed species) and taxa with more expressed head sculpture under T. semilaeve complex (at least two unnamed morphospecies and T. galaticum Menozzii, 1936). For proper identification of all taxa nest samples with males and gynes are required. In our material from Thrace we have three species from T. depressum complex (T. hippocratis, T. cf. depressum sp. 1 and T. cf. depressum sp. 2) and at least one species from T. semilaeve complex (T. cf. semilaeve). We managed to collect only one nest sample of T. semilaeve complex and it belongs to an undescribed species which seems to be widespread in Greece. Probably most literature records of T. semilaeve from Greece concern this undescribed taxon. True T. semilaeve André, 1883 is distributed only in western part of Mediterranean basin (Borowiec et al. 2015).

Doubtful published records
Legakis 2011 listed five species from Thrace which are probably based on misidentification or misinterpretation.

Discussion
Although Thracian ant fauna has been almost totally neglected thus far, we can consider this Greek region as relatively diverse. We collected 115 species, only 7 already mentioned in the checklist in Legakis 2011. Other five taxa mentioned in this checklist can be treated as doubtful records and they probably concern species found also by us, but we cannot specify their true identity without checking voucher specimens. Thus, in total we can confirm the presence of 115 ant species for Greek Thrace. Out of the 11 geographic regions of Greece, only Macedonia with 158 species has richer ant fauna, while Dodecanese, East Aegean Islands and Ionian Islands have similar number of registered species (Borowiec & Salata unpubl. data). One reason for high species richness in Greek Thrace is probably the geographic position of the region, which is situated between the Aegean Sea and the Rhodope Mountains. As the result, we can encounter here species which are otherwise more common in the southern Greek regions, islands of eastern part of Aegean Sea or Aegean part of Turkey (e.g. Since they belong to taxonomically problematic groups it is very possible that they have already been recorded under different names from other parts of the country. Many ant genera and species groups are taxonomically unresolved so we cannot give the exact names for several species from the checklist. Some of them probably have available specific or infraspecific names now trated as synonyms of different taxa, and some are probably taxa new to science. Results of the present study and recent investigations from other parts of the country show great richness of Greek ant fauna. Based on the material we have collected from various parts of Greece and which includes many still unidentified taxa (Borowiec & Salata unpublished data), it is estimated that at least 320 ant species occur in the fauna of Greece, several of them new to science.