Informace o publikaci
Chironomidae of spring fens: mechanisms driving compositional changes on local and regional spatial scale.
|Popis||Spring fens represent unique aquatic habitats of high conservation importance. Only remnants of former large complexes can be found throughout Central Europe and also in some boreal area of Scandinavia. These remaining areas are still seriously threatened by fragmentation, degradation and destruction, despite their high biological value. They usually provide shelters for many rare and endangered species and can act as refugia for climatic relicts. Chironomidae are one of the most diverse and species-rich taxonomic groups inhabiting these unique habitats. Altogether, we found 76,554 individuals belonging to 105 taxa at 64 spring fens in the Western Carpathians with average of 25 taxa (980 individuals) per site. Studied sites were small-sized helocrenes, isolated from each other and relatively homogeneous in within-site hydrochemistry and vegetation composition. However, considerable differences in flow conditions defined two extreme mesohabitats at sites: the flowing- (A) and the standing-water (B). Quantitative samples were collected from each mesohabitat in April/May and September/October in 2006-2012. Chironomids´ assemblages mainly responded to flow conditions (amount of dissolved oxygen and water temperature) at both mesohabitats. The main ecological gradient of fens, the gradient of mineral richness, significantly influenced assemblages at the flowing-water; at the standing-water type of substratum was more important. Both mesohabitats provided suitable conditions for Chironomidae, we did not find any significant differences comparing within-site alpha diversity (between A and B). It is not surprising, when one considers the high species diversity of chironomids. Species inhabiting fens differ in their ecological demands and thus are able to colonize all types of available microhabitats. Nevertheless, there were significant compositional differences between the flowing- and the standing-water and using novel method of beta diversity partitioning the species replacement was identified as the leading force of beta diversity differences. This might result from evolutionary adaption for both flowing- and standing-water environment by various chironomid species. The niche-based processes determined structuring of chironomids´ metacommunities at regional spatial scale (ca 200 km). Involvement of spatial based processes was manifested only at longitudinal and latitudinal gradient, although not significantly. Subsequently, chironomids were classified according their habitats specialization and commonness, as dispersal abilities of different species cannot be considered as the same in such diverse group. The only group with significant spatial structuring was common species due to possible mass effect. The results suggest that even poor dispersers and/or highly specialized species were able to overcome natural barriers and colonize suitable spring fens. The study was financially supported by Czech Science Foundation P505/11/0779.|