Earthworm Populations (Oligochaeta, Lumbricidae) in the Basin of the Middle Reaches of the Bol'shaya Laba River (Northwestern Caucasus, Buffer Zone of Caucasian Nature Reserve)

The species composition and structure of the population of earthworms in the forest and meadow formations in the basin of the middle reaches of the Bol'shaya Laba River are studied for the first time. The species of the Crimea and Caucasus are unusually rare. The erosion topography in combination with significant precipitation results in increased heterogeneity of habitats and in the formation of specific taxocenoses with respect to a hydromorphic or automorphic soil regime. The Crimean-Caucasian subendemic Dendrobaena schmidti, which is the dominant on the northern macroslope of the Great Caucasus, is replaced in automorphic soils by the Easteuro-Asian D. tellermanica, a nemoral-steppe parthenogenetic species, which is well-adapted to a high-amplitude regime of temperature and humidity. Hydrophilic and non-frost-hardy species become numerous in hydromorphic soils. The relationship between the structure of earthworm populations and the soil water regime is illustrated well by the abundance ratio of morpho-ecological forms, among which no anecic are registered. The necessity to protect middle-mountain ecosystems of the northwestern Caucasus as a refugium of Mediterranean earthworm species is shown.