Close non-murid rodent species in the fauna of Ukraine: differences, biogeography, and ecomorphology

Abstract

Close non-murid rodent species in the fauna of Ukraine: differences, biogeography, and ecomorphology. -I. Zagorodniuk. -Results of taxonomic revisions, analysis of identification criteria, spatial and ecomorphological differentiation of close pairs of species are summed up. Increased taxonomic heterogeneity is characteristic for 4 superspecies: Spermophilus suslicus s. l. (2 species), Sicista subtilis s. l. (2 species), Sicista betulina s. l. (2 species), and Spalax zemni s. l.(2 species). Unlike other groups of small mammals (in particular, bats and rodents of the superfamily Muridae s. lato, seu Muroidei), all these superspecies complexes are represented by allospecies. Accordingly, the differences between them by eco-morphological characters are minimal or absent. It was revealed that sympatry in each group is possible only with species from adjacent taxa of the same ecomorphological groups, in particular, susliks with marmots, forest birch-mice with steppe birchmice, and mole rats with mole voles. In all these allospecies complexes, all species are related to the foreststeppe or steppe faunal complexes (except for the northern forest birch-mice from the superspecies Sicista betulina s. l.), as well as their spatial differentiation is based on the principal inter-river spaces, and the boundaries of their ranges are large watercourses. One of the key factors of spatial segregation is the delimitation by large rivers, first of all the Dnipro, Dnister, Tyligul, Molochna, and Donets. Cases of sympathy, even marginal, have not been revealed, but the analysis of ancient literature and collections show signs of recent expansion of species. In particular, signs of the expansion of Spermophilus odessanus to the west were detected; probably the same applies to Sicista loriger and Spalax zemni. The key biogeographic coordinate of the whole complex of "small" species of non-Muroidei rodents is the Lower Dnipro, in particular the triangle between the Lower Dnipro, the Black Sea, and the Molochna river. Guilds in all these groups are as simple as possible (practically mono-species), and in addition, three of four of these groups are presented by hibernating animals (fourth group is underground rodents). Unlike other groups of mammalian siblings, all analyzed species do not show any tendency to synanthropy and are in need of special conservation measures. K e y w o r d s : rodents, non-Muroidei, taxonomy, distribution, differences, ecomorphology.

Range dynamics in sibling species: facts and reconstructions for the mammal fauna of Eastern Europe

“…(Zagorodniuk, 2002 b). Important factors in reconstructions are the non-random spatial distribution of chromosomal numbers, the fact that both karyotypes of "speckled" ground squirrels (odessanus with 2n = 36 and suslicus with 2n = 34) are derived from the initial 2n = 36 known in pygmaeus, and the configuration of distribution ranges of these species (Zagorodniuk, 2019) allowing to suggest their dispersal from the Azov Region.…”

“…These new areas could also include those that were previously inhabited by a neighbouring species. Such range dynamics was clearly facilitated by the significant ecomorphological similarity of all ground squirrel species of this group (Zagorodniuk, 2019) and also intensified by an extremely narrow spatial niche. The latter is determined by the adherence of ground squirrel settlements to slopes of small river valleys (ibid.…”

“…We support a different view, namely a hypothesis on the formation of a steppe faunal core in the Lower Dnipro area as a derivate of eastern steppe complexes, particularly of North Caucasian, Dagestanian, and Trans-Volga steppes (Zagorodniuk, 1999). Such a complex, the core of which was named Dnipro Endemic Group, DEG (Zagorodniuk, 2019), comprises five strictly steppe species of mammals with a distribution restricted in the west by the Dnipro River: Microtus socialis, Sylvaemus whyterbyi, Spermophilus pygmaeus, Scirtopoda telum, and Spalax arenarius. The last species is the only one considered here a distinct species, while the others are subspecies of more eastern species.…”

“…In case of the sandy mole rat, the eastern species would be S. giganteus with which it forms a single group "giganteus" (Topachevsky, 1969;Korobchenko, Zagorodniuk, 2009). An important step in proving this hypothesis was the recent identification of a subfossil specimen of Spalax from Askania Nova as S. arenarius (Zagorodniuk, 2019): this fact is in favour of the secondary nature of the current restricted range of S. arenarius and its formerly wider eastward distribution in the Azov Region closer to S. giganteus.…”

“…The last of them has the most recent (since 1997) and most complicated taxonomic history as well as a unique geographical range restricted by coastal regions and the Lower Dnipro area (Zagorodniuk et al, 1997). Based on chorological data, the species was included into the Steppe Faunal Core (Zagorodniuk, 1999), particularly to its central segment which also includes species of DEG (sensu Zagorodniuk, 2019). The uniqueness of the latter is its most recent appearance in the region from the east.…”