Elements of meta-community structure of birds on the border of south taiga and forest-steppe of Trans-Urals (Russia): the effect of the environment gradient, spatial processes and interspecific competition

To identify the general principles of the assembly of natural communities is a fundamental issue of community ecology. To date, four paradigms have been formulated, within the framework of which the structure of meta-community and its providing factors are studied. Among the most important processes influencing the meta-community structure several processes are emphasized. These are random processes, those determined by the environment and those determined by biotic interactions. In the article we discuss the role of ecological gradients, non-environmental spatial processes and interspecific competition in the formation of bird communities on the border of taiga and steppe of Trans-Urals. From 2000 to 2011 we collected the information on the species composition of nesting birds of 17 sites. The meta-community structure was described using the element analysis method of the meta-community structure - EMS. To give accent to the main environmental gradients PCA method was used. To assess the impact of non-environmental spatial processes the correlation analysis of the similarity of the species composition of the sites and the distance between these sites was conducted. The role of competition was studied by comparing the variance of differences in body size of birds both within definite sites and within the regional species pool. For the statistical verification of a hypothesis the observed indices were compared with random ones calculated using the fixed model (FF). The leading process of the formation of the structure of the birds’ meta-community on the border of taiga and forest-steppe of Trans-Urals is species sorting along ecological gradients. The structure of the meta-community of birds in the studied area within the sites least modified by anthropogenic activity corresponds to the Gleason gradient. The Gleason meta-community structure correlates well with the main ecological gradient. Community nesting is not revealed. The hypothesis about the role of interspecific competition is not confirmed. Minimal differences in body size of birds were not revealed. For the orders of Passeriformes and Falconiformes body size aggregation is characteristic. The role of spatial processes in the formation of the bird population is not significant. The correlation between the similarity of the species composition and the distance between the sites is not significant.