Mole-rat from Khortytsia in the light of morphological and geographical relations between Spalax zemni and S. microphthalmus

The taxonomic status of the mole-rats from Khortytsia Island which is located between the ranges of Spalax zemni (right bank of the Dnipro) and S. microphthalmus (left bank) are considered. This island population is a unique biogeographical phenomenon that may be an evidence of ancient evolutionary events associated with the migration of steppe animals in the region of Zaporizhia Rapids. The mole-rat forms on Khortytsia a stable population, which is regarded as autochthonous. Osteological characters of mole rats from the island and adjacent areas of the right bank of the Dnipro, as well as comparison of these samples with those of S. zemni and S. microphthalmus from distant parts of their ranges were investigated. By all characters, mole rats of Khortytsia and adjacent areas of the left bank of the Dnipro should be identified as S. zemni. Authors suggest that the mole-rat population in the nearest left-bank steppes may also be S. zemni. Descriptions of craniological characters to distinguish the two species and their distribution map are presented