Ants (Hymenoptera, Formicidae) of the Kyraiskaya depression of the Southeastern Altai

32 species of ants were revealedin the Kuraiskaya Depression, from which 26 species were found in the forest meadow landscapes, 12 species  in mountain-depressionsteppe landscapes, 8  in high mountain, and only one species  in mountain tundra. 70% of fauna (25 species) are common with Tuva,55% (23 species) are common with Mongolia. Similarity of faunas is the result of high concentration of different conditions within thesmall (comparing to Tuva and Mongolia) Kuraiskaya Depression. Treeless landscapes are totally dominated by Formica candida F.Smith; it penetrates forest borders, and highlands of up to 2800 m a.s.l. Its population in the depression near foot of mountains (up to 25nests/25m2) is maximal for the areal in general. With each altitudinal belt the population number decreases with the increasing steepnessof landscape; and the lowest number is registered on the slopes. The decrease in number of F. candida is also observed with lowering ofthe absolute altitude of landscape from mountain slopes to the valley of the Chuya River. Landscape monodomination is determined byecological flexibility of the species and, probably, by the absence of competitors among xerophiles, which lets us assume the conditionsof the steppe depression be optimal for this species. Species, living nearby F. candida (F. pratensis Retzius, F. uralensis Ruzsky , F.sanguinea Latreille, F. exsecta Nylander, F. lemani Bondroit, F. pisarskii Dlussky, F. brunneonitida Dlussky, F. subpilosa Ruzsky)inhabit mainly hollows, north-faced slopes, forest margins and sandy spits, they almost do not reach the flat surfaces with the steppetype of vegetation. Occurring in subalpine and alpine steppes F. fusca Linnaeus, F kozlovi Dlussky prefer forest margins, F. gagatoidesRuzsky  hollows and benches, whereas F. candida inhabits mostly warmed sites with rare herbage. The exception to this is rubblysteppe slopes in mountain tundra, where Leptothorax acervorum Fabricius occur in mass (12 nests per 25 m2). Distribution of F. candidain the Kuraiskaya Depression, as well as in Southern Tuva and SE Transbaikalia, can be called landscape domination. This factallows supposing that conditions of the mentioned steppe depressions are optimal for this species. We revealed the same domination ofthe desert steppe species (Cataglyphis aenescens (Nylander) и Proformica mongolica Emery) earlier in the Chuiskaya Depression, SEAltai, which is more arid with prevalence of desertificated mountain steppe landscapes. Among the steppe landscapes under considerationfrom highlands to the bottoms of depression the ants population has two zones of the highest number: highland (tundra-meadowsteppe)and at the turn of the low part of a mountain range and the upper area of a foothill plain. This corresponds to the data on othergroups of invertebrates including those of collembolan of Tuva.

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