Fauna, Ecology and Biotopic Distribution of Earthworms (Oligochaeta, Lumbricidae) in the Upper Altitude Zones of the Northeastern Caucasus

A large-scale mosaic of environmental conditions is a characteristic feature of mountain regions. The species composition of the earthworm fauna and the number of species are closely related to local and regional environmental conditions. Also, it is unknown how this relationship manifests itself in species outside their ecological optimum—in the upper altitude zones of mountains. The aim of the work was to study the earthworm fauna of the Dagestanian variant of altitudinal zonation in order to assess the influence of altitude and local (large-scale) environmental factors—“relief and exposure,” “altitudinal belts,” “phytocenosis” and “soil moisture source.” Eleven species (twelve taxa) of earthworms were collected at altitudes of 1400–2670 m a.s.l. For each species, the Standardised Selectivity Index and Standardised Ecological Niche Breadth were calculated. The dependence of the earthworm population composition on both altitude and local conditions (relief, soil moisture regime and type of vegetation cover) was observed. Twelve taxa of earthworms were found to effectively use the available ecological space at high altitudes. This is due to the diversity of ecological strategies they use, based on different physiological and behavioural adaptations.