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The role of environment and dispersal mode in metacommunity structuring of aquatic invertebrates at isolated spring fens.
|Popis||Recent explanation of the processes driving ecological metacommunities aim to integrate two opposing paradigms: (1) Species exhibit different environmental niches and ecological communities are consequently structured by habitat features (species sorting paradigm); (2) Species are environmentally equivalent and ecological communities are therefore determined by species dispersal abilities (neutral model). It has been proved that relative importance of these two processes differ among different types of metacommunities and spatial scales, nevertheless no study has been conducted at spring fens so far. Available predictions are based on previous studies from headwater streams and expect prevalent effect of abiotic factors in this environment. Spring fens are unique aquatic habitats primarily for their very stable environmental conditions and specific communities of organisms with high proportion of habitat specialists. Furthermore, they are highly isolated from each other and can be regarded as islands in surrounding terrestrial matrix, thus dispersal abilities can significantly affect species composition of particular assemblages as well. In this study of 59 springs from the Western Carpathians (ca 200 km), five taxocenosis were compared considering their different dispersal abilities (from the poorest dispersers: Clitellata, Ephemeroptera, Plecoptera, Trichoptera, Chironomidae). However, dispersal abilities can differ even within these taxocenosis (rare vs. common species, specialists vs. generalists). For instance, the importance of dispersal- and niche-based processes for specialists and generalists is almost unexplored due to difficulty of defining specialists in the aquatic environment. In contrast, specialists inhabiting spring fens can be easily defined as species strictly bound to this environment, unable to colonize surrounding aquatic habitats. We expected important spatial structuring of passive dispersers, habitat specialists and also common species due to possible mass effect. Our results showed prevalent influence of environmental factors for almost all groups which supports findings from previous studies. We found substantial difference between passive (Clitellata) and active (Insect) dispersers with only significant effect of environment factors for all insect taxocenosis. The strongest spatial structuring was proved in Clitellata specialists, on the other hand insect inhabited suitable sites regardless habitat specialisation. Our predictions about spatial structuring were all confirmed; moreover generalists divided into passive and active dispersers showed significant spatial patterns as well. Dispersal mode (active/passive) was the decisive criterion giving priority to one of the models, neither species’ specialisation nor rarity. This study was financially supported by Czech Science Foundation P505/11/0779.|