SPIDERS (ARANEI) OF THE PERIGLACIAL LANDSCAPES OF THE TSEI GORGE, NORTH OSSETIA-ALANIA, CAUCASUS, RUSSIA

Abstract

In the framework of a comprehensive study of arthropods taking part in the primary successions of the periglacial landscapes in the North Caucasus, spiders were collected from 10 sites of different ages (ranging from 1 to 170 years) in the upper reaches of the Tsei Gorge at altitudes of 2071 to 2336 m a.s.l. As the glacier retreats, meadow communities are formed at the site of bare near-glacial areas, these being first replaced by shrubs in areas aged 10–14 years, and then by forest communities on 30–35-year old surfaces. Spiders appear almost immediately after the retreat of the glacier, and representatives of at least three families are found already in the area that was freed from ice just a year ago. This pioneer complex consists not only of representatives of the alpine fauna, but it also includes species without pronounced altitudinal preferences. However, the primary assemblage is short-lived, being completely replaced in 10–15 years, especially sharp rearrangements of the spider populations being noted during the transition from meadow to the forest stage of succession. In 30–35 years following the retreat of the glacier, the spider complexes reach a level of diversity that is quite comparable with that in developed communities of the mountain forest belt. A comparison of the periglacial assemblages of Caucasian spiders with those formed under similar conditions in the southern and northern mountains of Western Europe indicates a profound regional specificity not only at the level of species, but even at the level of families.