Pelobates balcanicus Karaman, 1928

Dufresnes, Christophe, Strachinis, Ilias, Tzoras, Elias, Litvinchuk, Spartak N. & Denoel, Mathieu, 2019, Call a spade a spade: taxonomy and distribution of Pelobates, with description of a new Balkan endemic, ZooKeys 859, pp. 131-158 : 143-144

Pelobates balcanicus Karaman, 1928

Diagnosis.

Resembling P. syriacus with which it was previously considered a synonym ( Frost 2019). Large toad with whitish metatarsal spades and a flat skull. Sexes of similar size (Fig. 2). Various motifs with gray, yellow or greenish colors, but rarely brown (unlike the sympatric P. fuscus , P. Székely pers. comm.); frequently specked with orange dots, sometimes heavily (perhaps more than in P. syriacus ) (Fig. 4). Based on 25 biometric characters, Uğurtas et al. (2002) showed that the P. balcanicus populations from the Balkans are morphologically very variable and differentiated from Asia Minor ( P. syriacus ); yet P. syriacus populations from European Turkey (Edirne, genetically confirmed by Dufresnes et al. 2019b) and southeastern Bulgaria (Primorsko) grouped with P. balcanicus ( Uğurtas et al. 2002). Roček (1981) only found one cranial difference: the processus posterior parasphenoidei is present in P. syriacus but not developed in P. balcanicus . Morphometric assessments associated to genetic data are needed. Based on populations of P. balcanicus balcanicus , average SVL = 67 mm (48-100 mm) for females (n = 16 populations) and 68 mm (46-94 mm) for males (n = 15 populations) (Suppl. material 1, Table S1; Fig. 2). The karyotype ( P. b. balcanicus ) consists of six large and seven small pairs of two-armed chromosomes. NORs (secondary constrictions) are in the short arm of pair 7 ( Belcheva et al. 1977). The nuclear DNA content (calculated from flow cytometry) averages 7.9 pg ( Litvinchuk et al. 2013; data from P. b. balcanicus ). As shown in Table 1, P. balcanicus differs from P. syriacus by ~7.4% at mtDNA and ~0.31% at nuclear DNA ( Dufresnes et al. 2019b).

Taxonomy.

Originally described as a subspecies of the Eastern spadefoot, Pelobates syriacus balcanicus Karaman, 1928; type locality: Dojran Lake, North Macedonia; type(s): most likely include the skeleton described by Karaman (1928), deposited at MMNH (Skopje, North Macedonia), but destroyed in an earthquake in 1963 (V. Sidorovska pers. comm.); the MMNH currently hosts one specimen from the type locality, MMNH-A-699 (collected in 2001). This taxon represents a distinct species from P. syriacus , due its old divergence (>6 My) and the absence of contemporary introgression at their area of contact in European Turkey, consistent with advanced reproductive isolation ( Dufresnes et al. 2019b). Therefore, we herein remove P. balcanicus from its previous synonymy with P. syriacus .

Distribution.

Pelobates balcanicus is restricted to the Balkan Peninsula, 0-920 m a.s.l. ( Džukić et al. 2008) (Fig. 1). In the north, it is present in northern Serbia and northwestern Romania. It follows the Danube River from Serbia to the Black Sea in Romania ( Székely et al. 2013; Ţeran et al. 2017). There are yet some possible gaps along the Danube (e.g. around the Iron Gate: Vukov et al. 2013; Ţeran et al. 2017). In the north-west, the Great Morova River in Serbia marks its western margin ( Džukić et al. 2008). Northern ranges are currently disconnected from the southern populations ( Vukov et al. 2013) of North Macedonia, eastern Albania (a single location), south-west Bulgaria (Strimon River), and Greece ( Džukić et al. 2008; Mollov et al. 2006; Szabolcs and Mizsei 2017). In the 1980s, Sofianidou (2012) reported the species along the western coastline of the Adriatic Sea and the northern coastline of the Gulf of Corinth (Greece), but there is no recent observation in this region. Elsewhere in Greece, it is present in Peloponnese ( P. balcanicus chloeae ssp. nov., see below), in the eastern parts of the mainland, and along the Aegean Sea shores, from Sterea Ellas to the Evros River, until it reaches P. syriacus in Thrace ( Džukić et al. 2008; Sofianidou, 2012). The spadefoots known from the Maritsa (Evros) River in southern Bulgaria, and along the western coasts of the Black Sea, may correspond to P. syriacus (Stojanov et al. 2011; Dufresnes et al. 2019b). IUCN status: Not Evaluated; previously included in P. syriacus assessment.

Diversity.

Using mtDNA and genomic data, Dufresnes et al. (2019b) evidenced a Pleistocene split (~2 My) for spadefoots from the Peloponnese ( P. balcanicus chloeae ssp. nov.). In the rest of the range, at least three glacial lineages (<1 My) were identified: a first one in the eastern ranges, from the Carpathians to the Black Sea and as south as Greek Thrace; a second one in western ranges from Serbia to northern Greece; and a third one on the coastal island of Evia (north-east of Peloponnese). The eastern and western lineages widely admix. Populations from central Greece are yet to be examined.