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The investigation examines the structure of diploid and polyploid populations within the spined loach group (Cobitis elongatoides-taenia-tanaitica) in the water systems of Western and Central Ukraine, including the Danube River, Dniester River, Southern Bug River, Vistula River, Middle and Upper Dnipro River basins. The study reveals a bipolarity in settlement structure, with a sharp prevalence of either diploids or polyploids, and no discernible geographical trends in spatial distribution. Clonal hybrid polyploids, which make up 70 % of the individuals studied in the region, are most common in settlements along the main river channels, as well as in the middle and lower reaches of first and second-order tributaries. Populations where diploid specimens of the parent species are predominant are located in accessory systems, tributaries of the third and higher orders, upper reaches of first and second-order tributaries, and lakes. This spatial segregation arises from historical circumstances rather than ecological preferences, primarily due to the distance from water corridors through which polyploids invaded in the 1960s-1970s. The displacement of diploid individuals by clonal hybrid polyploids is a universal phenomenon. This is due to the advantages of parthenogenetic reproduction and higher survival rates of polyploids in modern environmental situations. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Genetic divergence and evolutionary shift of transitions and transversions ratio were analyzed based on examples of 60 sequences of the mtDNA control region of 27 species of mice (Murinae) of the Palearctic region. Representatives of Cricetidae and Arvicolidae were taken as outgroups. The constructed phenogram corresponds to the accepted phylogenetic scheme and is clustered according to population, semispecies, allospecies, species, genus and family levels of divergence. In the phyletic order there is a clearly defined evolutionary transition/transversion rate bias. Its distinction is an extremely fast and abrupt transition from dynamic to stable phase. The dynamic phase is a rapid decrease in the ti/tv rate ratio and refers to the population and semispecies divergence levels. The stable phase refers to the species level and higher divergence levels and is associated with reaching a state of genetic saturation in a situation of predominance of transversions. The extreme denotion of the evolutionary shift in the D-loop case can be explained by the removal of the selection pressure caused by restrictions in amino acid substitutions. This means that the causes of transition/transversion bias are purely biochemical mechanisms on DNA level. Simultaneously, the stability of the ti/tv ratio at species and higher levels amidst the further accumulation of the total number of nucleotide substitutions may indicate a fundamentally different nature of genetic processes at the intraspecies and interspecies levels of divergence. [ABSTRACT FROM AUTHOR]

The comparative analysis of fecundity and fertility was studied experimentally for the amphimictic Aporrectodea caliginosa diploid and the close parthenogenetic A. trapezoides triploid earthworms during two seasons. The in dividual fecundity of cocoons at is signific antly higher in the parthenogenetic species than in amphimictic one. Fertility is in contrast lower in the parthenogenetic species, which results in leveled parameters of the reproductive potential. A generalization and analysis of the available data on the comparative fecundity of representatives of different animal groups shows that the automatic increase in fecundity in samesex organisms due to the exclusion of males cannot be considered a universal rule providing biological progress and the ecological advantage of parthenogenetic organisms. This explanation is not suitable for hermaphroditic organisms. In addition, in some cases, parthenogenetic reproduction is accompanied by reduced fertility and even reduced fecundity. [ABSTRACT FROM AUTHOR]

An analysis of 11 diploid-polyploid samples of the spined loaches of the Cobitis of the aquatic systems of Ukraine showed that the increase in the number of micronuclei in the erythrocytes is positively correlated with the ploidy and cell size. In diploid individuals of parental species, micronuclei cells are on average 0,12 %, whereas hybrid triploids are 0,52 %, tetraploids are 1,39 %, and probable pentaploids are 4,72 %. Since triploid and tetraploid specimens in joint colonies tend to dominate diploid, it can be concluded that minor violations of the genetic apparatus, do not significantly affect on the fitness. Whereas an increase in the number of chromosomal sets over four is already accompanied by dysfunctions critical to normal life activity. This circumstance, obviously, has led to the absence or extreme rarity of the pentaploid states in the clonal vertebrates, whereas in the lower invertabrates, for example earthworms, the usual are penta-, hexa- and octo- and decaploid states. The latter is probably due to the fact that the minimum size of the genome in the earthworms is some times of magnitude smaller than that of teleosts, which allows lower invertebrates to increase the number of chromosomal sets more than four times. [ABSTRACT FROM AUTHOR]

Four chromosomal races (2n=36, 3n=54, 6n=108, 8n=144) and 96 clones have been revealed among 224 specimens of the earthworm A. rosea over the territory of Ukraine by means of karyological analysis and biochemical genetic marking. Each population has been showed by several clones at least; moreover the clones from different places have never been identical. The clones in the range of one population can be identified with the set of quantitative and qualitative parameters. [ABSTRACT FROM AUTHOR]