First Record of the Inquiline Ant Leptothorax kutteri Buschinger , 1965 from Turkey

Ant societies typically are protected against intruders or parasites through a highly efficient system of nestmate recognition. Nevertheless, numerous species of arthropods and other animals have evolved mechanisms of invading the nests of ants by masking themselves with or mimicking the recognition cues of their hosts. In addition to myrmecophile beetles, crickets, flies, etc. (Kronauer & Pierce, 2011) this includes the socially parasitic ants, i.e., ants that rather than establishing their own colonies temporarily or permanently rely on the support of workers from other ants species (Buschinger, 2009). Inquiline ants have the most derived life history of social parasites, as they have completely lost or greatly reduced the worker caste (Buschinger, 2009). Queens of many inquiline ants live alongside the host queen and host workers and produce only sexual offspring, while host workers take over all daily duties, such as brood care, foraging, and nest defense. Because of their strict dependence on host ants, inquilines typically can be found only in dense Abstract We report on the occurrence of the ant Leptothorax kutteri Buschinger, 1965 in two sites in Northern and Eastern Turkey. Leptothorax kutteri is a workerless inquiline living in the colonies of L. acervorum (Fabricius, 1793) so far known from various parts of Northern and Central Europe. Our findings greatly increase the range of this small and rare ant. Sociobiology An international journal on social insects


Introduction
Ant societies typically are protected against intruders or parasites through a highly efficient system of nestmate recognition. Nevertheless, numerous species of arthropods and other animals have evolved mechanisms of invading the nests of ants by masking themselves with or mimicking the recognition cues of their hosts. In addition to myrmecophile beetles, crickets, flies, etc. (Kronauer & Pierce, 2011) this includes the socially parasitic ants, i.e., ants that rather than establishing their own colonies temporarily or permanently rely on the support of workers from other ants species (Buschinger, 2009).
Inquiline ants have the most derived life history of social parasites, as they have completely lost or greatly reduced the worker caste (Buschinger, 2009). Queens of many inquiline ants live alongside the host queen and host workers and produce only sexual offspring, while host workers take over all daily duties, such as brood care, foraging, and nest defense. Because of their strict dependence on host ants, inquilines typically can be found only in dense host populations, and spotting the few inquiline queens among the host ants is often difficult. Our knowledge about the occurrence and distribution of inquilines is therefore incomplete and novel findings are worth of being mentioned.

Materials and Methods
During the survey of the ant fauna of Turkey we found two colonies of L. acervorum containing very small queens, female sexuals, and pupae. One nest (12/3071b), with one dealate queen and three winged female sexuals, was found on 12.08.2012 in a very old Pinus sylvestris L. and Picea orientalis (L.) forest under a stone at Şavşat, Arsiyan Plateau (Artvin prov., N 41˚24′ 26″, E 42˚28′ 09″) at 2214 m (Fig 1). The other colony (13/3684c), with one winged female sexual, was found in a very old P. sylvestris and Abies nordmanniana (Steven) Spach forest in a rotten pine tree trunk on 24.08.2013, Mesudiye, Arıkmusa Village (Ordu prov., N 40˚24′ 37″, E 37˚55′ 24″) at 1914 m (Fig 2), 385 km WSW of the first site. Colony 13/3684b contained also a morphologically aberrant male. Table 1 lists other ant species found in these two sites.  Mounted specimens were measured using a Keyence VHX-500FD digital microscope at 200x magnification following the definitions of various measures given by Seifert (2018). The collected material is deposited in the Entomological Museum of Trakya University (EMTU), Turkey.

Results and Discussion
The small queens and female sexuals found in colonies of L. acervorum in Turkey closely match the original description of L. kutteri by Buschinger (1965), photos of this species (Blatrix et al., 2013;Borowiec, 2006;Seifert, 2018) and also mounted queens and female sexuals of L. kutteri collected near the type locality in 1994 (collection J. Heinze) in their small size and the presence of a pronounced ventral, postpetiolar tooth (Fig 3). The measures of most traits of Turkish specimens (Table 2) are in the range given by Seifert (2018) for L. kutteri from Europe, and disagreements, e.g., in head shape and mesosoma width, might be due to different instruments and slightly different methodology. The propodeal spines of the Turkish samples (propodeal spine index appr. 1.6) are similar in length to those in specimens from the type locality and Switzerland (propodeal spine index 1.4-1.6, Kutter, 1967), but shorter than those in L. kutteri from Massif Central (propodeal spine index 1.94, Blatrix et al., 2013).  In contrast to the type material, the discoidal cell in the forewing of female sexuals is closed by a well-developed transverse medio-cubital vein in three individuals from both collecting sites. Furthermore, the frontal area between clypeus and median ocellus is more heavily sculptured (Fig 4) than reported for the type and specimens from Sweden (e.g., see https://www.antweb.org/bigPicture.do?name=antweb1041 362&shot=h&number=1).
Like L. kutteri from Europe, the specimens from Turkey differ from the other two recognized palearctic inquilines of L. acervorum, L. goesswaldi Kutter, 1967 and L. pacis (Kutter, 1945) in their shorter and less dense hairs and a less concave clypeus with a straight anterior margin.
The male found in the colony from Mesudiye Arıkmusa Village was strikingly different from previously reported males of L. acervorum, L. kutteri, and other inquiline species (Fig 5). Its petiole and postpetiole had a very peculiar, inflated shape, which resembled those found in teratological phenotypes of L. acervorum (Fig 36 in Buschinger & Stoewesand, 1971;Dekoninck et al. 2012).
As sequencing of the mitochondrial genes CO I/CO II failed due to the presence of nuclear copies (unpublished results), it cannot be excluded that a closer morphological and genetic examination might reveal the Turkish material to form  a phylogenetic lineage distinct from other populations of L. kutteri. Inquilines have been suggested to evolve sympatrically within the populations of their hosts via intraspecific parasitism and queen size polymorphism (Buschinger, 1990;Bourke & Franks, 1991;Savolainen & Vepsäläinen, 2003). Leptothorax acervorum is one of the two ant species with the widest native geographical distribution (e.g., Heinze & Hölldobler, 1994;Schär et al. 2018) and it is therefore not surprising that inquilinism has evolved repeatedly. This is evidenced by the occurrence of the two other inquilines of L. acervorum but also by a striking polymorphism of chromosome numbers between L. kutteri populations from the type locality, Sweden, and the Alps (Buschinger & Fischer, 1991) and considerable morphological variation in different populations in Finland (Saaristo, 1995). In case additional collection revealed the "morphologically aberrant" males to be the regular males of the inquiline, the hypothesis that the Turkish specimens belong to a novel species would clearly have to be reassessed. At present we consider the single male to be a deformed phenotype and conclude that the Turkish specimens are L. kutteri. This greatly increases the range of this species, with the geographically closest population in Southeastern Poland (Radchenko & Czechowski 1991) more than 1600 km to the Northwest of the sites in Turkey. Other inquilines found in the nests of Leptothorax also appear to have a surprisingly wide range: L. goesswaldi, originally known from the French and Swiss Alps and Scandinavia, has been documented in East Kazakhstan (Schultz & Buschinger, 2006), and L. wilsoni Heinze, 1989, first described from New Hampshire, New Brunswick, and Québec, has also been found on the other side of the continent, in Montana, Alberta, and Alaska (Buschinger & Schumann, 1994;www.antweb.org).