Vol 44, No 10 (2017)

A biogeographical division of northern Eurasia (within the USSR borders as of 1991) based on cluster analysis of the cyclostome and fish fauna composition at 597 sites listed in the Biodat database has been performed. The classification based on the Jaccard similarity coefficients included two regions, 12 subregions, eight provinces, and 11 districts. The division performed explained 67% of the variance of the similarity coefficients, this being 21% higher than the respective value for an earlier scheme (Berg, 1962) that covered a significantly greater territory. Correlation with the climatic regimes and environmental factors identified could explain 82% of fish fauna heterogeneity (the multiple coefficient of correlation was 0.91). The nonorthogonal relations with the temperature regime (67% of the variance of similarity coefficients), landscape and climatic zoning (58%), location within a specific river basin (57%), and provinciality (30%) were the most important factors.

The patterns of change in the calendar dates of the start, end, and duration of wintering of the common spadefoot toad (Pelobates fuscus) in the Medveditsa River valley (Lysogorskii district, Saratov oblast) in the period from 1892 until 2014 are considered. A reduction in the duration of wintering by seven days due to a shift in the start of wintering to a later date and that of the end of wintering to an earlier date (on average) over the last 120 years is shown. The changes in the end and start of wintering mainly began to emerge in the 1950s and 1980s, respectively, and significantly accelerated in 2002–2014. The periodicity of changes in the dates of the start and end of wintering occur mainly owing to the winter severity cycles (8–9 years) and the humidity–aridity ones (Brückner cycle of 36–38 years). Our analysis of the temperature regime across the soil profile shows that the shortening of wintering is mainly caused by the earlier start of the spawning migration of mature individuals of this species in the spring. The depth of location of P. fuscus individuals in the soil profile has decreased steadily from the early 1980s to 2014. Predictive models have been developed allowing us to forecast the termination of movement of P. fuscus individuals in the soil profile from the horizons where they can be found in the period of activity by 2050, as well as a significant reduction in the wintering duration or even its complete disappearance as a phase of the annual cycle in the course of 315 years provided that the modern climatic trend will continue.

The vitality of 31 natural populations of Tulipa gesneriana is based on our field surveys that were conducted in several parts of European Russia from 2013 to 2015. The basic factors that affect the vitality of the T. gesneriana population were revealed according to the results of the analysis of 14 morphological parameters of T. gesneriana. Cattle grazing was the most essential factor. The effect of other negative factors is much lower. On the whole, the mixed stress-tolerant and ruderal ecological cenotic strategy is characteristic of the species. For instance, an increase in the stress level leads to a decrease in the size of all aboveground organs, which is accompanied by considerable variations in the height and diameter of plants. However, most of the parameters, on the contrary, have a weak reduction in their variability under stress. All these features indicate a comparatively narrow ecological amplitude of the species investigated.

Reproductive success demands both the male and female reaching a particular physiological status, which is usually stimulated in rodents by certain olfactory signals. The hormonal response of male Eversmann’s hamster (Allocricetulus eversmanni) to the natural excretions (urine, midventral gland secretion (MVGS) of conspecific females was studied during several seasons of the year, with the animals kept in conditions of natural lighting and temperature. In the fall, no reliable changes in the testosterone level in males in response to any signal presented were noted. In the winter and spring, a reliable (P< 0.05) increase in the testosterone level was caused by the female MVGS odor. In the summer, a similar reaction only to conspecific female urine (P< 0.05) was noted. Moreover, in the summer and fall, males showed a reliable decrease in the cortisol level in response to the odor of female urine (P< 0.05). In the winter and spring, a similar result was caused by exposure to both odors. The progesterone level in males reliably (P< 0.05) increased upon exposure to both female urine and MVGS in all seasons of the year, except for the female MVGS in the summer. Therefore, the decreased cortisol level in combination with the simultaneously increased testosterone and progesterone levels allow the males of the species under study to achieve their maximum reproductive success, despite the high degree of their intraspecific aggression.

The results of study of the quantitative and qualitative composition of arthropod communities at potential nesting areas of great bustard (Otis tarda) in the Saratov Trans-Volga region are reported. Specific data collected at seven areas (two plowed fields, two fields of winter and spring wheat, two fallows of different ages, and virgin land) in 2012 are presented. Comparative analysis of some parameters of arthropod abundance and biomass on chemical-treated and untreated winter crop fields has been conducted. The results obtained have been compared to those of previous years. The current conditions for rearing of nestlings on natural fallow lands of different ages and on early-spring crop fields in the Saratov Trans-Volga region during the nesting period of O. tarda are favorable. The abundance and composition of arthropods in winter crop fields treated with a complex of chemicals do not meet the requirements for the rearing of O. tarda nestlings.

This paper presents data on the polymorphism of inter simple sequence repeats of DNA in the silver crucian carp Carassius auratus gibelio in water bodies in the southern part of Western Siberia. The share of polymorphic ISSR-PCR bands in silver crucian carp populations from different lakes varied from 40 to 70%, and Nei’s gene diversity index varied from 0.16 to 0.25. The genetic diversity indices were lower in the populations that were largely represented by females than in bisexual ones. The highest levels of genetic polymorphism were revealed in populations with diploid–triploid complexes. The gene diversity index of the silver crucian carp population is positively correlated with the reservoir size (r = 0.90, p = 0.015; Rs = 0.74, p = 0.036).

This paper examines the influence of the location of settlements, railroads, and highways on the spatial structure of the Otis tarda population in the Trans-Volga region that was studied in the years 1998–2016 in a model area of 12000 km² that is located in the southern part of the Saratov Trans-Volga region. The zone of the impact made by our estimated disturbance factor due to the movement of people and a variety of ground vehicles along various-purpose roads on the territorial distribution of bustards in autumn can be denoted as a 300–500 m width band on both sides of the transport communications. Shelterbelts that were created along transport communications render a beneficial effect on the distribution of O. tarda and reduce the influence of the disturbance factor. Furthermore, crop rotation fields with side sizes of more than 1 km can be considered a factor that compensates for the anxiety of birds. We have found that in the Saratov Trans-Volga region, because of the large size of crop rotation fields and significant development of roadside and shelter belts, no special measures are required to protect O. tarda such as restrictions on the movement of people and vehicles over the territory where this species lives.

The features of Uralian saiga habitats are discussed. Periods of high and low abundance of the animals, which alternate depending on the productivity of vegetation communities and territorial humidity (the number of watering places) due to climate changes, are shown. After periodic cases of the mass death of saiga, their population is quickly restored to its previous level, which is likely to be facilitated by the existing feed and water resources.

A typical feature of the populations of small mammals in different areas of the Saratov Trans-Volga region is the long-term and constantly increasing abundance of Sylvaemus uralensis and its wide distribution in a variety of habitats. The maximal abundance of S. uralensis is 72.0 individuals per 100 trap-days, and its share in catches is 73.0%. The abundance of Microtus arvalis tends to increase. It was shown that Lagurus lagurus has been found again in the steppe zone, on fallow lands and fields, after a prolonged depression in 2012–2013, the average density of species being 4.0 individuals per 100 trap-days. A high abundance of other typical steppe inhabitants (Allocricetulus eversmanni and Ellobius talpinus) was noted as well. The highest indices of species diversity (H = 1.18) are typical of fallow lands.