Chorology of Spalax arenarius, an endemic rodent species of the Lower Dnipro Sands and Taurida steppe

Abstract

The article analyses one of the most unique species of mammals in the fauna of Ukraine—the fossorial rodent Spalax arenarius. The sandy mole rat is an endemic of the Ukrainian Black Sea region, one of the two endemic species in the mammal fauna of Ukraine and also a species having the smallest geographic range among representatives of the East European mammal fauna. The specifics of the modern distribution of this species, its morphological features and differences from the neighbouring species, from which it can be considered a derivative, are analysed. Particular attention is paid to five aspects of the chorological analysis: 1) description of the current distribution with a detailed map of the species’ occurrence; 2) analysis of ancient Spalax specimens and the former distribution of this species based on actual data; 3) determination of the actual range boundaries, primarily along the land, i.e. in the east of its distribution, 4) analysis of the probable reasons for the range restriction from the west as a probably recent expansion to the region; and 5) construction of a model of the formation of the current range based on re-constructions of the distribution of Spalax in the Taurida Steppe. The latter was carried out considering the morphological features of Spalax arenarius, which are most similar to those of Spalax giganteus, whose modern range is limited to the Caspian Sea regions and, apparently, the North Caucasus. According to morphology and habitat reconstructions, the sandy mole rat is most likely a sister species to Spalax giganteus and one of the source forms for the western S. zemni (similar to the history of ground squirrels). The unique features of the Lower Dnipro population are presented, including the colouration of the feet and rhinaria and the structure of the skull. The history of the Lower Dnipro settlement is considered in view of the regular flooding of the region in historical times (including the flood of 2022). The hypothesis of a recent (possibly secondary) expansion of the species into the region and the specifics of its presence and absence in other neighbouring territories, in particular in the Crimea, Syvash, and the Molochnyi Estuary area, are formulated and considered. The sands zone is most likely the area of recent expansion of the species, which demonstrates a correspondence to the entire complex of Lower Dnipro isolates, including Microtus socialis, Sylvaemus witherbyi, and Scirtopoda telum.