ALBERT

Description:    Mollusc communities of previously unexplored Bulgarian fens were studied in order to determine and generalise the patterns of species richness and composition along the mineral richness gradient. The aim was also to compare predictive values of the environment, vegetation and spatial structure. Altogether, 44 mollusc species were recorded at 40 treeless fen sites. Species richness varied from 0 to 18 species per site, and it was positively associated with the mineral gradient and negatively with altitude. However, the best predictor was obtained using plant species composition. All explanatory variables had higher effect on land snails than on the entire mollusc assemblage (including aquatic species). Species richness and abundance were significantly and positively correlated with the species composition turnover; the communities were highly nested, with poor sites having subsets of the fauna found in the richest. The main direction of mollusc species turnover was highly associated with that observed for vegetation, and the main gradient of plant species composition was able to explain nearly 20% of total variation in mollusc data. We found that spatial structure explained by far the highest proportion of independent variation, which reflected the high level of geographical isolation of Bulgarian fens and regional differences independent of any environmental variation. Our results demonstrate (1) the general role of mineral richness gradient for structuring mollusc communities in fens, (2) the pivotal indicator role of plant species composition in predicting species composition of mollusc communities, despite being trophically independent and (3) the effect of isolation and origins of the habitat on species composition: most species have wide geographical distributions within the habitat type, and geographical patterns within Bulgaria may have a stochastic element. Content Type Journal Article Pages 1-11 DOI 10.1007/s00114-011-0816-x Authors Michal Horsák, Department of Botany and Zoology, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic Michal Hájek, Department of Botany and Zoology, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic Petra Hájková, Department of Botany and Zoology, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic Robert Cameron, Department of Animal and Plant Sciences, University of Sheffield, Sheffield, S10 4TN UK Nicole Cernohorsky, Department of Botany and Zoology, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic Iva Apostolova, Department of Phytocoenology and Ecology, Institute of Botany, Bulgarian Academy of Sciences, Sofia, Bulgaria Journal Naturwissenschaften Online ISSN 1432-1904 Print ISSN 0028-1042