Olga Rostovskaya’s research while affiliated with I.I. Schmalhausen Institute of Zoology and other places

A study of taxonomic differentiation and transition bias of the cytb gene, focusing on the early stages of speciation, was carried out in 15 subfamilies/families of five orders of Palearctic mammals. It was confirmed that the genetic differentiation among taxa of small and large mammals is shifted by the same taxonomic level, in which connection the period of cryptic speciation of Micromammalia (semi- and allospecific levels) corresponds to the divergence of type species in their genus within Macromammalia. In all cases, both transition bias and its evolutionary compensation took place. The novelty of the study also lies in the proof that the alignment of the transitions and transversion rates in evolutionary lineages has the pattern of a phase transition, and the frequency of transversions in short-cycle species of the orders Insectivora and Rodentia is higher than in long-cycle orders Artiodactyla, Carnivora and Chiroptera while with relative equality of transitions. The latter circumstance might be associated with the traits of metabolism and determines the characteristics of the molecular evolution of mammalian groups with short and long life cycles.

Geographic peculiarities of population structure and hemicloning reproduction of the water frog Pelophylax esculentus complex of 904 samples within southern East European Plain were analyzed. The proportion of populations of P. ridibundus is 0.667 against those 0.042 of P. lessonae . The RE-type populations are the most common among mixed ones (0.153). The colonies of the two parental species and P. kl. esculentus (REL-type), as well as those of P. lessonae with P. kl. esculentus (LE-type), have the frequencies 0.072 and 0.046, respectively. All-hybrid populations (E-type) are not numerous across the region (0.017). In the populations of Central, Northern and Western Ukraine, the P. lessonae genome is eliminated during gametogenesis within hybrids while in the Lower Dnieper and Lower Danube drainages, genome of P. ridibundus is eliminated. In the Eastern Ukraine populations, hybrids usually produce diploid gametes or haploid gametes with the P. ridibundus genome, less often with the chromosome set of P. lessonae only, and even more rarely a mixture of different types of gametes. The predominance of P. ridibundus in hybrid communities and the elimination of the P. lessonae genome in hybrids inevitably leads to the transformation of hybrid populations into “pure” R-type populations. This circumstance makes hybridization with P. ridibundus a factor in the shrinking of P. lessonae populations. That trend is especially expressed in the Forest steppe zone, where hybridization proceeds most intensively, the P. lessonae genome is eliminated in hybrids, and unstable populations with a numerical superiority of P. ridibundus predominate.