Microprotrusion variability of demographic and shell parameters in Helicopsis striata populations (Mollusca; Pulmonata; Hygromiidae) in the South of the Mid-Russian Upland

The аdaptation of species populations to heterogeneous environmental conditions is accompanied by formation of their specific spatial patterns. The aim of this work was to study microspatial structure of populations in the protected steppe snail Helicopsis striata (Muller 1774). For this, we analyzed the variability of shell and demographic features in six model populations of snails from heterogeneous conditions of the South of the Mid-Russian Upland (see Tables). In each population, the material was collected in autumn from five localities (dems) that are situated at a distance of 150-200 m from each other. We determined that on the territory of H. striata studies there are two types of spatial population structure. A highly-differentiated structure is characterised by frequent and significant changes of individuals' density, metric parameters and shell pattern throughout the saiga range. Such structure is established for the populations "Belaya gora" and "Belenikhino" (the Seversky Donets basin river) at the same time having the greatest variability of quantitative features of shell and its pattern. A low-differentiated structure is characterised by less significant and more gradual changes of the studied parameters. It is typical of other populations with medium or low variability of shell parameters. With that, there is temporal stability of population structure according to the variability of quantitative shell features. On the basis of the obtained results we have established the relationship of population spatial differentiation with their living conditions. Thus, the most structured populations of H. striata are situated in more moist conditions of the Seversky Donets basin river. On the other hand, the nature of population structure does not have a clear connection with the degree of the biotope heterogeneity. Along with different optimum density in populations with different types of partition, this may indicate its dependence on the state of population gene pools. Analysis of the shell pattern phenotype in population dems allows revealing the dependence of their frequencies on the environmental factors. For example, there are more albinos in populations and dems that live in habitats with frequent outcrops of chalk. On the other hand, the increase in the proportion of albinos in the population may be associated with a reduction of genetic diversity by inbreeding and genetic-automatic processes. We noted that the originality of the spatial differentiation of demographic and conchological variability parameters in populations of H. striata from the Seversky Donets basin river can testify in favor of their belonging to a different taxonomic group. The article contains 4 Figures, 6 Tables, 24 References.

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