[The formation of new characteristics in life cycle of the marsh frog (Rana ridibunda) in thermal pond conditions].

Using mark and recapture approach, the long-term population dynamics in the marsh frog (Rana ridibunda) was studied. Group-marking of metamorphs was conducted in a small thermal pond serving as a sedimentation basin for discharged waters from Nizhny Tagil metallurgic works. Depending on the time of metamorphosis, three groups of individuals could be singled out, namely: early ones (group I), middle ones (group II), and late ones that overwinter as tadpoles and complete metamorphosis in May of the next year (group III). Upon metamorphosis completion, individuals of group I were found to be significantly larger than those of group II, and individuals of both these groups to be significantly smaller than those of group III. After first wintering, immature individuals from group I were significantly larger than either individuals from group II or metamorphs from group III, though a growth rate of the latter was significantly higher than in groups I and II. These discrepancies were observed both between immature and adult individuals. Over the period from metamorphosis completion to the first wintering ending, survivorship in group I was significantly higher and did not differ between groups II and III. In adult frogs, maximum survivorship was registered in group III and minimum one in group II; the detected differences recurred in each age class till the fourth wintering. However, in age classes that overwintered 4 and 5 times, maximum survivorship was observed in group II, which can be treated as a compensation for rather low survivorship of this group at younger ages. All the events of tadpoles of this species overwintering (except in other thermal water bodies) that are described in literature, correspond to rare deviations from normal ontogenesis. Therefore, the revealed formation of a numerous group of overwintering tadpoles in successive generations should be considered as a new adaptation which sense is a decrease of competition between tadpole groups when using the highly productive resources of the thermal pond practically year-round. The advantage in body size and growth rate of not only tadpoles but also of metamorphs, immature and adult individuals of group III indicates that after metamorphosis the strategy of this group still remains successful. The reason for that is unusually large body size of metamorphs which provides higher postmetamorphic survivorship and greater female fecundity.

[Geographic variation of sexual dimorphism in the moor frog (Rana arvalis) as a result of differences in reproductive strategies].

Several local populations of the moor frog (Rana arvalis) from the southern part of the range (the Ukraine) were compared by size and age composition and morphological characters in males and females with one of the populations from Moscow Region (Zvenigorod Biological Station-ZBS). In spite of close geographical location of the Ukrainian populations (not more than 40 km), they differ significantly both in mean body size and age. At that, mean value of these parameters turned out to be lower than the corresponding values for the ZBS population. In southern populations, the proportion of females breeding for the first time right after the second hibernation is higher than males; comparing to the ZBS population, the part of two-years-old mature specimens of both sexes is higher while the part of older specimens is lower. This geographical variability of age composition causes significantly lower mean age and body size of specimens from the southern populations. Although in the Ukraine the activity season is longer than in Moscow Region, the growth rate of two- and three-year-old frogs from southern populations is lower, and only at age of four they become larger than specimens from the ZBS population. These differences are caused by higher reproductive effort both in females and males from southern populations. Morphologically, males and females from southern populations differ most significantly by shin and hip length (absolute and relative values of the characters are higher in males). As compared to the Ukrainian populations, both sexes in the ZBS population have lower values of these characters. The overall sex differences by absolute and relative values of these characters are more pronounced in the ZBS population. Meanwhile, concerning body size, males are bigger than females in the ZBS population, and this difference remains and is even more pronounced in the southern populations. Geographic variation in body size is more expressed in females than in males, which corresponds to more significant sex differences in the Ukrainian populations in this regard. The reason behind this lies in dissimilarity in reproductive strategies: males from the ZBS population participate in the breeding for the first time at younger age than females whereas in the Ukrainian populations males take part in reproduction at older age (hence, at bigger size) which ensures their greater reproductive success.

[Geographic variation as a result of evolution of the traits with broad and narrow norms of reaction in the moor frog (Rana arvalis)].

Females reproductive, size, and age characteristics were studied in isolated local populations of Rana arvalis in the southern and northern parts of its range. The yearlings of the southern populations used to get larger by their first overwintering due to earlier beginning of the breeding season, as compared with the yearlings of the northern population. As a result, "southern" females become sexually mature at the age of two years while the "northern" ones become mature at the age of three years. This causes geographic differences in age composition among two populations, the "southern" reproductive females being younger on average than the "northern" ones. The earlier female maturation in the first case is not compensated by respective rise of the growth rate; to the contrary, the "southern" females grow more slowly during the first two years of their life and appear to be smaller than the "norhern" ones. These reproduction and growth patterns arise supposedly due to paedomorphosis, which causes specific reproductive characteristics, namely decrease in the egg size, increase in the reproductive effort and more strong correlation between female fertility and body size. Local and geographic differences are expressed not in the extent but in the structure of reproductive pattern, as no negative correlation was revealed between female reproductive age and body size in the southern populations. Southern habitats cannot be considered as "unfavourable with respect to body size", so the geographic differences under consideration cannot be explained by optimization of the reproductive strategies at population level. Paedomorphosis appears as a result of the female maturation rate possessing a wider norm of reaction than the growth rate. At the same time, fixation of the specific growth rate narrows norm of reaction of some other characters important for the phenotype reproductive fitness thus predetermining their subsequent evolution.

[The correlation of the ecological niches of the common (Rana temporaria L.) and of the moor (Rana arvalis Nilss.) frogs (Anura, Amphibia)]. / Sootnoshenie ékologicheskikh nish travianoi (Rana temporaria L.) i ostromordoi (Rana arvalis Nilss.) liagushek (Anura, Amphibia).

During 25 years ecology and population dynamic of two brown frog species (Rana temporaria and R. arvalis) were studied in Moscow region, Solovki island and South Ural. We compared life cycles characteristics, namely biotope preferences, diet, migration, enemies, hibernation places using own and available literature data. Then we analyse how these parameters are changed among the species area and ecological niches were compared. We found that these two species do not compete in any stage of life cycle. Ecological niches are very closed and differences are determined generally by abiotic factors. So, R. temporaria prefers more wet biotope and more sensitive to acidity (low pH value). Differences in spawning time do not associate with interference in spawning places. We conclude that interspecific competition did not take place neither in the past nor in present and the reason of differences in ecological niches are determined by separate ways of evolutionary development of these species.