The edible frog, Pelophylax esculentus, is a hybrid form that reproduces via clonal propagation of only one of the parental genomes through generations of hybrids while the genome of other parental species is eliminated during gametogenesis. Such reproductive ability requires hybrids to coexist with one of the parental species or rarely both parental species causing the formation of so‐called population systems. Population systems and reproductive biology of water frogs from the east of the range remained partially unexplored. In this study, we investigated the distributions, population systems, genetic structure, types of gametes, and morphological variability of water frogs of the genus Pelophylax from the northeastern parts of their ranges (Mari El Republic and adjacent territories, Russia). We examined 1,337 individuals from 68 localities using morphological traits combined with DNA flow cytometry and a multilocus approach (fragments of a nuclear and two mitochondrial genes). We revealed five types of population systems: “pure” populations of the parental P. ridibundus (R) and P. lessonae (L), mixed populations of parental species (R‐L) along and with their hybrids (R‐E‐L), as well as mixed populations of P. lessonae and P. esculentus (L‐E). However, the “pure” hybrid (E) and the mixed P. ridibundus and P. esculentus (R‐E) population systems were not found. All hybrids studied by DNA flow cytometry were diploid. Analysis of gametogenesis showed that the majority of hybrid males, as well as hybrid females from the L‐E system, produced gametes with the P. ridibundus genome. However, in the R‐E‐L system, hybrid females were usually sterile. The reproduction of hybrids in such systems is primarily based on crosses of P. esculentus males with P. lessonae females. Molecular analysis showed the presence of mitochondrial and nuclear DNA introgression of the Anatolian marsh frog (P. cf. bedriagae) into both P. ridibundus and P. esculentus. The observations of alleles and haplotypes of P. cf. bedriagae in P. ridibundus and P. esculentus individuals from the same localities suggest de novo formation of local hybrids. However, the presence of the Balkan marsh frog (P. kurtmuelleri) haplotypes in local hybrids supports the hypothesis regarding the migration of old hemiclonal lineages from glacial refugia. Finally, the diagnostic value of various morphological characteristics was discussed.

The article is devoted to the analysis of changes in the structure of the territory of Kazan in the period from the 18th century to the present. The spatial and temporal variability of the main functional zones of the city is considered. The main ways of expanding the territory of the city and its constituent functional zones related to the main historical processes are given. The total area of the city, according to cartographic analysis, increased 77.04 times in the period from 1739 to 2021. The article presents the dynamics of changes in the areas of the functional zones of the city during the period under review. The characteristic of ecosystems for the biodiversity of terrestrial vertebrates of the identified functional zones is given.

An analysis of the age structure of three water frog species (P. lessonae, P. ridibundus, P. esculentus) in the Middle Volga region of Russia was conducted. The skeletochronological method determined their maximum lifespans to be 7, 6, and 4 years, respectively. This study revealed specific characteristics of the age structure of Pelophylax frogs in relation to their taxonomic composition when cohabiting (population system type) and the degree of habitat transformation. Differences in body size and lifespan were observed among cryptic forms exhibiting mitochondrial DNA replacement and the presence of various types of heterozygous and homozygous alleles. Water frogs of the genus Pelophylax have a complex taxonomic structure, including hybrid species and morphologically cryptic forms, as well as massive mitochondrial DNA introgression. The aim of our paper was to analyze the age structure of three species of water frogs (P. lessonae, P. ridibundus, and P. esculentus) in the Middle Volga River region (European Russia). Based on the skeletochronological method, we determined their maximum lifespans of seven, six, and four years, respectively. The onset of sexual maturity in the marsh frogs occurred after two and four winterings in males and females (respectively), in the pond frog—one to two years, and in the edible frog—one to three years. This study revealed specific characteristics of the age structure of Pelophylax frogs in relation to their taxonomic composition when cohabiting (population system type) and the degree of habitat transformation. Differences in body size and lifespan were observed among cryptic forms exhibiting mitochondrial DNA replacement and the presence of various types of heterozygous and homozygous alleles.

The article describes the methodological approaches used to study the influence of major international sportingevents on the development of the city and region (on example of XXVII World Summer Universiade which heldin the Russian Federation in the city of Kazan in 2013). This paper presents the results of economic, social andenvironmental consequences for the development of the city of Kazan and Tatarstan. Assessment of impacts isgiven in an integrated form, with the conclusions of the contradictory effects for the different areas of the cityand the region.