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S V Mezhzherin

Publications and source records attributed to S V Mezhzherin.

At least 19 recordsLinked to original sources
PubMed2004

[Natural transfer of nuclear genes in hybrid populations of green frogs Rana esculenta L., 1758 complex: space-time analysis of the phenomenon].

Spatial and temporal analysis of frequency distribution patterns of the Rana esculenta (=lessonae)-specific allele, Ldh-B71, in the populations and individuals of R. ridibunda from the Middle Dnieper region was performed. It was established that the allele was accumulated in the populations of Kiev, where on average 15 to 25% of individuals steadily preserved this allele through at least three to four generations. Furthermore, the allele frequency in juveniles and adults was similar. These findings suggest that the frogs carrying foreign genetic material were not eliminated from the populations, and hence, the observed introduction of foreign genes was adaptively neutral. The transfer of the genetic material from one species to another may be considered as a possible mechanism of the formation of an additional source for population genetic variation, which, however, do not seems to be evolutionary progressive.

Alleles↗
PubMed2002

[Genetic structure of a diploid-polyploid complex of the spined loach Cobitis taenia (Cypriniformes: Cobitidae) from the middle Dnieper bassin].

Biochemical genetic typing and cytometry showed that polyploid females account for 87% of the spined loach Cobitis taenia population from the middle Dnieper basin. The polyploidy series included triploids, tetraploids, and, possibly, a few pentaploids. A characteristic feature of the genetic structure of polyploids was that their genetic variation was due to the clonal variation in the haploid portion of the genome originating from Cobitis sp. and to polymorphism of the diploid portion originating from C. taenia. The results are discussed with regard to comparative evolution of alloploid complexes in fish and terrestrial vertebrates.

Animals↗
PubMed2002

[Correlation between variability and body size in vertebrates].

An analysis of allozymic variation carried out in the main groups of vertebrate animals revealed a tendency towards the increased level of genetic polymorphism in the species of small animals compared to the large ones. This tendency was clearly followed in caudate amphibians, fishes, and mammals. The data are discussed in terms of the integration of monogenic and polygenic systems in the populations. It is hypothesized that this relationship between heterozygosity and body size confirms more general regularity consisting in highly statistically significant correlation between polygenic heterozygosity, maturation rate and life span. It is suggested that high rate of development in small animals resulting in early sexual maturation, can serve as a mechanism determining correlation between heterozygosity and body size at the species level. As a result, compared to large animals, small animals display higher rates of generation change, resulting in accelerated growth of population size and faster accumulation of genetic variability.

Animals↗
PubMed2002

[Variation of loci encoding homologous enzymes in an evolutionary series of vertebrates].

A study of variability of 11 allozyme loci (sAat, G3pdh, Gpi, sIdh, Ldh-A, Ldh-B, sMdh, sMe, sSod, Pgdh, and Sdh) in the evolutionary series of vertebrates from Cyclostomat to Mammalia revealed that (1) in vertebrates, these loci encoding multimeric enzymes are characterized by different heterozygosity levels, the extremes of which (represented by loci Ldh-A and Pgdh) differ from each other more than by a factor of 4; (2) classes of vertebrates markedly differed from one another in genetic variation; lower Tetrapoda are characterized by the highest level of genetic polymorphism, the classes representing the margins of the phyletic line-primitive (Cyclostomata and Chondrchthyes) and advanced (Aves and Mammalia)--have minimum heterozygosity levels, whereas Osteichthyes are characterized by intermediate heterozygosity level; (3) in the evolutionary series of vertebrates, heterozygosity varies rather independently in the groups of loci characterized by low, medium, and high variability. These patterns are explained in the context of intraorganismic factors: integration of mono- and polygenic traits (primarily, body size and ontogeny rate) and evolutionary specialization.

Animals↗
PubMed2000

[Genetic structure of species community of macromycetes of the genus Leccinum Gray (Basidiomycetes, Boletaceae) of the right-bank Poles'ye].

The biochemical gene marking of the macromycete community of the genus Leccinum revealed nine reproductively isolated genetically differentiated forms instead of 2-5 forms traditionally recognized in Poles'ye. From 20 to 85% of the loci studied were found to have genetic distinctions and the degree of genetic variation did not always correlate with the morphological features of the forms identified. The variation of the locus number was found to be an important differentiating factor characteristic for this genus. In the group of L. scabrum s. I., every second locus was duplicated, whereas multiple isozymes were absent in L. aurantiacum s. I. The extremely high level of allozyme variation in macromycetes was found. The equilibrium between the expected and observed genotypes in the fruit body samples was established and discussed. It was the evidence of the fact that a panmictic model can be applied to the mushrooms of this genus, and that each fruit body is an individual organism.

Basidiomycota↗
PubMed1999

[Genetic connections and differentiation of ground squirrels Marmotinae Pocock, 1923 (Rodentia, Sciuridae) from Palearctics].

Genetic distances between eight species of sousliks (Spermophilus) and five species of marmots (Marmota) were estimated on the basis of 39 biochemical loci. All taxa were shown to be genetically discrete. The genetic differentiation was minimal (Pfd = 11.3) between parapatric species of Palearctic sousliks of the suslicus pigmaeus group and Marmota species, intermediate (Pfd = 34.7) between allopatric sousliks species, and maximal (Pfd = 56.7) between representatives of different genera. The following trends were revealed in the geographic differentiation of the genus Spermophilus: (1) genetic similarity was associated with the geographic distance; (2) the eastern and western Palearctic phyla were markedly different genetically; (3) the eastern Palearctic forms exhibited higher differentiation than the western ones. The revealed speciation pattern is consistent with the general trend of temporal differentiation in Palearctic phyla and confirms the periodic speciation mode in the Palearctics.

Animals↗
PubMed1998

[Allozyme variation of lactate dehydrogenase (EC1.1.1.27) in a series of vertebrate animals].

An allozyme variation of loci-encoding lactate dehydrogenase was compared in different vertebrate classes. A lower level of heterozygosity in warm-blooded as compared to cold-blooded vertebrates was shown. The highest heterozygosity was revealed in anurous and caudate amphibians; the lowest, in birds and mammals. Fishes and reptiles exhibited an intermediate level of heterozygosity. In higher groups of vertebrates, differences in the electrophoretic mobilities between alleles decreased. A key aspect of this is a hiatus of these differences in fishes and mammals. On the basis of this analysis, the following conclusions may be drawn: (1) the rate of amino-acid substitutions in homologous proteins is unequal in distant phylogenetic lineages; (2) the level of heterozygosity is related to the average amount of electrophoretic allelic differences at the class level; (3) significant differences in variation pattern in the phylogenetic lineage of vertebrates is probably associated with the evolutionary features of the genomic organization of groups at different evolutionary levels.

Alleles↗
PubMed1997

[Genetic differentiation and phylogenetic relationships among Palearctic mice (Rodentia, Muridae)].

Genetic differentiation of 18 Palearctic mouse species (genera Sylvaemus, Mus, Apodemus, Micromys, and Rattus) with respect to 31 biochemical loci was estimated to define the taxonomic status of these genera. On the basis of genetic data, two independent centers of origin of species belonging to the family Muridae were identified. The first is the Indo-African center, from which the modern Sylvaemus species and Palearctic representatives of Mus originated in the Pleistocene (1.0-2.0 million years ago). Genera Micromys and Apodemus, which diverged in early Pliocene (about 7 million years ago), trace their origin to the same center. From the second center, located in Southeast Asia, Rattus species radiated. The genetic divergence of taxa issuing from these two centers attains the level characteristic of differentiation between families and dates back to the late Miocene (over 10 million years ago). Species were compared pairwise to determine the percent of fixed gene differences (Pfd) between them. Analysis of Pfd distribution confirmed distinct periodicity of speciation in mice and revealed two speciation peaks. The first, at the level of genera, occurred in the Pliocene, and the second, at the species level, in the Pleistocene.

Animals↗
PubMed1997

[Gradualism or punctualism: data on genetic differentiationof small mammals from the Holarctic region].

Genetic differentiation of taxa from three Holarctic and three originally Afrotropical phyla of small mammals was analyzed. Its extrapolation to the time scale revealed the following trends: (1) Distributions of fixed gene differences along the scale are relatively independent. (2) Extrapolation of these distributions to the time scale shows that the speciation process is discontinuous. It consists of relatively stable periods interrupted by speciation bursts. (3) Periods of speciation activity in different phyla coincide. In general, these results are consistent with the concept of punctuated equilibria and suggest that the speciation process is temporally discontinuous.

Animals↗
PubMed1997

[Gene diffusion in hybrid populations of green frogs Rana esculenta L., 1758 complex (Amphibia, Ranidae) from the Dnepr Basin].

Population-genetic analysis of hybrid populations of green frogs from the Dnepr basin demonstrated limited gene introgression in diploid hybrids in addition to semiclonal reproduction, which is typical for Rana esculenta hybrids. Introgression is largely confined to the Ldh-B locus: the gene of R. lessonae is introduced into the R. ridibunda genome. This phenomenon is unstable as it is geographically restricted and absent in populations of the E-L type.

Animals↗
PubMed1995

[Genetic structure and origin of the tetraploid toad Bufo danatensis Pisanetz, 1978 (Amphibia, Bufonidae) of Central Asia. Differentiation of geographic forms and genetic relationship between diploid and tetraploid species].

A hierarchical system, consisting of several levels of genetic divergence, is formed by distribution of genetic distances between diploid taxa of the green toad species complex (subspecies Bufo viridis viridis--B. v. turanensis and species B. viridis--B. sp.) and taxa representing western (B. viridis s.l.) and eastern (B. raddei) Pale-arctic regions. Formally, genetic differentiation of the tetraploid toad B. danatensis from the parapatric diploid species reaches the species level. Genetic diversity of the tetraploid species is more than twofold higher than the total diversity of two modern diploid species. This suggests that B. danatensis was formed with the participation of other unknown species in the past. The polyploid species B. danatensis is assumed to have originated by hybridization of two species groups that arose approximately 2.6 million years ago in Mediterranean and Central Asian regions of the western Palearctic. The genetic heterogeneity of geographical populations of the polyploid species indicates its polyphiletic origin. The heterogeneity range suggests that formation of the tetraploid species continued for a very long period (about 1 million years).

Animals↗
PubMed1995

[Biochemical variability and genetic divergence of the palearctic voles (Arvicolidae): subgenus subterranean voles Terricola, true lemmings Lemmus Link, 1795, pied lemmings Dicrostonyx Gloger, 1841, steppe lemmings Lagurus Gloger, 1842, and mole voles Ellobius Fischer von Waldheim, 1814].

Genetic differentiation of 35 vole species, estimated at 18 to 31 biochemical loci, allowed us to identify the following phyla of the tribe level: Lemmini, Dicrostonychini, Ellobiini, Clethrionomyini, and Microtini. Average genetic differentiation between the tribes (D'Nei = 0.977) corresponds to separation of the phylogenetic branches in the middle Pleistocene. Tribe Lagurini was shown to be contained within Cletrionomyini. Ondatrini was the first branch that diverged from the common stem in the Miocene (D = 1.563), prior to the formation of the Arvicolidae family. Distribution of genetic distances indicates that family radiations comprised two stages, tribal (Pliocene) and specific (Pleistocene). Ages of the taxa, estimated by means of the molecular clock, agreed well with stratigraphic data. Marked periodicity of divergence in the family confirms the concept of punctuated evolution.

Animals↗
PubMed1995

[Genetic structure and origin of the tetraploid toad Bufo danatensis Pisanetz, 1978 (Amphibia, Bufonidae) from Central Asia. Biochemical polymorphism and comparison of the level of heterozygosity of diploid species with tetraploid species].

Comparison of individual variation at 24 biochemical loci in members of the species complex of Palearctic green toads showed that the heterozygosity of the tetraploid species Bufo danatensis (Hobs + 0.45) was significantly higher than that of the diploid species B. viridis, B. sp., and B. raddei (Hobs = 0.009 - 0.103). Such difference can be explained only by a hybrid origin of the tetraploid species. Individual electrophoretic variability of the polyploid toad species is associated with an allelic variation that is manifested in constantly heterozygous spectra as the gene dosage effect. At the population level, this phenomenon found in Pamir toads is caused by irregular meiosis in founders of the population or by directional changes in gene regulation. Genotypic distributions in zones of contact of the diploid and tetraploid taxons demonstrate the possibility of restricted introgressive hybridization.

Animals↗
PubMed1992

[Genetic relationships between European and Transcaucasian mice of the genus Apodemus Kaup].

Genetic relations between four European mice species of the genus Apodemus (Apodemus sylvaticus, A. flavicollis, A. microps and A. falzfeini) and five Transcaucasian ones (A. mystacinus, A. microps, and the forms No 2, 3p, 3f) were studied for 37 biochemical loci. Close genetic relations were demonstrated between the mice of subgenus Sylvaemus and A. mystacinus. A. microps and A. falzfeini from the Caucasus were shown conspecific to these species from the Ukraine and the presence of the two new different species--the form No 2 and 3p in the Caucasus was established.

Animals↗
PubMed1988

[Genetic divergence of Mus musculus musculus and M. m. hortulanus].

Genetic divergence between house mouse and gleaner mouse from different regions of Ukraine was estimated by electrophoresis at 26 loci. Four diagnostic loci were established among these species: IDH-1, Est-1,2,4. Genetic distance between species is 0.217, which is in accordance with genetic differences between other species of the genus Mus. The results obtained give evidence that house and gleaner mouse are different species.

Animals↗