No 2 (2023)

We compared the reindeer forage stocks at two landfills in the southern part of the Yamal Peninsula for the period from the early 1930s to 2017–2019. Data from [30] was used to characterize the feedstock in the 1930s. Feedstocks in the 1930s and 2017–2019 in plant communities in the basins of the the Erkatayakha and Baidaratayakha rivers were compared in the following vegetation divisions: lichen and shrub tundras; moss and grass tundras; shrub tundra; meadow communities; and bogs. The following hypotheses were tested: (1) the total supply of feed in Yamal decreased since the 1930s; (2) the decrease in stocks affected the lichen component to the greatest extent. Both hypotheses were confirmed. The general changes in the stocks and structure of food in the plant communities of South Yamal over the 85–87 years include delichenization, a decrease in the mass of lichens and the proportion of lichen food. The average stock of lichen fodder from the 1930s to 2017–2019 decreased by 5 times in the communities at the Erkatayakha test site and by 2 times at the Baidaratayakha test site. The mass of green fodder for 85–87 years has not changed. Thus, the change in the masses of economically important components of tundra vegetation over a uniquely long period, almost 90 years, has been characterized.

The results of the study on the vertical distribution of abiotic characteristics and chlorophyll (Chl a) in the Gorky, Cheboksary, Kuibyshev, Saratov, and Volgograd reservoirs in the summer of 2021 are presented. The content of Chl a varied from 5.5–8.5 to >100 g/L in the Middle Volga to 22 and 47 g/L in the Lower Volga, and was typical for the summer maximum of phytoplankton in the Volga reservoirs. In the absence of density stratification for most stations, a uniform Chl a distribution in the water column was revealed with variation coefficients of no more than 20%.

Understanding the processes that affect the dispersal distance is essential from perspective of ecology and evolution. It is essential to understand processes that affect dispersal distances. Dispersal distances can may depend on environmental and demographic factors and on the motivation of an individual. Effective dispersal results in the distribution of related genotypes in space. The distribution of pairwise distances between related common shrews (sibs and half-sibs) is characterized by a nonrandom increase in the number of relatives at distances up to 200 m. Aggregations of relatives are formed in a part of individuals dispersed in a random direction to the nearest available home rang (“stright-line search”). The distribution of all distances between relatives (up to 1200 m) is satisfactorily approximated by the straight-line search model and is not consistent with the “spiral search” model as it is; however, the best match can be achieved by combining these two search types. The latter model variant (“mixed search”) assumes that the population includes animals with different personal traits: “superficial” and “thorough” explorers. Thorough explorers search for a vacant territory employing the spiral search strategy and correspond to “dreamers” in the model describing the movement and habitat selection strategy (MHSS). If vacant territories are in deficit and the environment is favorable, dreamers move over long distances and become randomly distributed in space: a random dispersion of related genotypes was recorded at distances from 200 to 1200 m. Therefore, searches for a dream territory in combination with a shortage of vacant territories (an accident) result in a random dispersal of related genotypes within a radius of at least 1200 m. The combination of temporal aggregations of relatives and the dispersal of related genotypes over a vast area explain well the previously discovered combination of an excess of homozygous alleles and a high allelic diversity.

A comparative study of lungworm Filaroides martis invasion rates in sable and pine marten populations in the Cis-Urals region and Central Siberia was performed on the basis of samples totaling more than 3000 animals. In different sable population groups, the invasion extensiveness (prevalence) varies from 2 to 57%; in pine marten population groups, from 0 to 54%. In the Urals transgression zone, the invasion rate is statistically significantly higher in martens compared to sables. The studied groups form three clusters. Low prevalence values (less than 2%) were noted in two eastern populations: the upper Ob River (martens) and the Vakh River (sables); the highest values (over 50%), in martens in the Urals and in both species in the Uvat district, Tyumen oblast. The rest of the groups with moderate prevalence values (20–38%) form the third cluster. The invasion intensity varies from 2.5 to 3.6 helminth cysts per infected individual in sables, and from 0 to 4.6 cysts in martens; for most pairwise comparisons performed based on these two parameters, differences between samples are statistically significant. In western groups of both species, the invasion intensity is higher compared to eastern groups. In sables, invasion prevalence and intensity correlate in a statistically significant (r = 0.95; p = 0.01) way. One geographical trend was identified: in pine martens, invasion prevalence increases in a northerly direction. Cases with prevalence levels less than 5% can be explained by the absence of formed filaroidosis foci. At the beginning of the 2010s, a twofold increase in prevalence over the previous 20 years was recorded; this phenomenon has no adequate explanation yet.

The results of studying the influence of the content of Ca2+, Mg2+, Na+, and K+ cations in water on the level of lipid peroxidation products and antioxidants in the tissues of bivalve mollusks, D. bugensis and D. polymorpha, are presented. Mollusks were caught in four water areas of the Gorky Reservoir, which differ in the concentrations of Ca2+, Mg2+, Na+, and K+ cations. A correlation relationship has been established between the quantitative parameters of cations in water and the intensity of peroxide processes, on the one hand, and the level of general antioxidant activity in mollusk tissues, on the other. Statistically significant interspecific differences in the studied parameters have been recorded in mollusks from areas with an increased concentration of cations.