[Population aspects of sexual dimorphism in guild of the Mustelidae: Mustela lutreola, Neovison vison, Mustela putorius, Martes martes as an example].

Size sexual dimorphism was investigated on 695 skulls of four Mustelidae species. By extent of increasing of differences between sexes the species are placed in following order: European pine marten (Martes martes), European mink (Mustela lutreola), American mink (Neovison vison), and European polecat (Mustela putorius). Extent of the dimorphism characterizes ecological plasticity of the species and is population characteristic. It is shown that M. martes takes specific and relatively narrow ecological niche of forest ecosystems, entering into weak competitive relationships with smaller Mustelidae species. The level of sexual dimorphism of M. lutreola, N. vison and M. putorius reflects intensity of its interspecific relationships within study area. High level of sexual dimorphism of M. putorius is determined by further divergence of ecological niches of males and females, and also appears to be compensatory mechanism reducing consequences of hardened environmental requirements.

[Odontologic anomaly in the American mink Neovison vison (Carnivora, Mustelidae) and possible reasons for its appearance].

The paper describes the phenomenon of substitution of the reduced M2 with a tooth of a complex structure in the American mink Neovison vison Schreber. The anomaly is observed on three skulls out of the 574 examined (0.52%) and is characterized by a clear localization, identical structure, and symmetrical manifestation. Atypical molars have two roots, equally well-developed paraconid, eokonid, hypoconid, and a less pronounced metaconid. Some possible hypotheses for the anomaly that are considered include disruption in the development of the dental germ, mutation, and phenotypic expression of genes that are characteristic of plesiomorphic species of mustelids. The substantiated viewpoint is that the cause of this phenomenon may be the "awakening of dormant genes" as a result of destabilizing selection and hybrid dysgenesis in the area of contact of farm and feral American minks.

[Patterns of morphological variability in reintroduced populations with two beaver subspecies Castor fiber orientoeuropaeus and Castor fiber belorussicus (Castoridae, Rodentia) as an example].

Taking as an example two beaver subspecies (Castor fiber orientoeuropaeus and Castor fiber belorussicus) with documented history of population formation, the patterns of morphological variability in translocated groups of mammals are studied. The variability of quantitative and qualitative traits in the formed populations is not characterized by a single direction. The main trend consists in increasing of adaptive norms diversity as related to body size. There observed a slight increase in the level of fluctuating asymmetry, reduction in polymorphism of nonmetric traits, and increase in fraction of rare aberrations. All these may be caused by inbreeding taking place during the period of prapopulations formation. The results of the study allow for considering the intraspecific differentiation as a consequence of adaptive variability (adaptatiogenesis) or subspecies hybridization. As for stochastic processes (genetic drift, founder effect), they seem to not influence the morphological variability significantly. The differences between discrete and dimensional traits are indicative of population groups' peculiarity.

[Introduction of species and microevolution: the European beaver, raccoon dog, and American mink].

Nine skull samples of the beaver Castor fiber, six samples of the raccoon dog Nyctereutes procyonoides, and six samples of the American mink Neovison vison were studied using phenetic and craniometric methods. Analysis of the phenofund structure suggests that in all of the studied species the emergence of novel character variations does not lead to their fixation with a significant frequency. Considerable morphological variability emerges in the contact zone of different autochtonous populations, of wild and breeding forms, as well as in geographically and reproductively isolated small groups of individuals. Morphological differences of introduced animals fit into the conception of species polymorphism and are smoothed over when separate colonies merge into metapopulations, which does not lead to the emergence of novel stable taxa.

[Polymorphism of the mitochondrial DNA control region in the population of raccoon dog (Nyctereutes procyonoides Gray, 1834) introduced into the Upper Volga basin].

Analysis of sequences (n = 30) of a hypervariable segment (599 bp) of the mtDNA control region in raccoon dog Nyctereutes procyonoides Gray, 1834, introduced into the Upper Volga basin, revealed a high level of molecular genetic variation. Two statistically significantly different haplogroups were identified. These haplogroups, however, were not associated with spatial geographic structure of the population. Phylogenetic patterns of the introduced population were associated with probable heterogeneity of autochthonous donor populations with respect to relatively large group of founders and a dramatic increase in the species number after the introduction.