Mollusc communities in Bulgarian fens: predictive power of the environment,vegetation, and spatial structure in an isolated habitat |
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Authors: | Michal Horsák Michal Hájek Petra Hájková Robert Cameron Nicole Cernohorsky Iva Apostolova |
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Institution: | 1.Department of Botany and Zoology,Masaryk University,Brno,Czech Republic;2.Department of Ecology, Institute of Botany,Academy of Science of the Czech Republic,Prague,Czech Republic;3.Department of Animal and Plant Sciences,University of Sheffield,Sheffield,UK;4.Department of Zoology,the Natural History Museum,London,UK;5.Department of Phytocoenology and Ecology, Institute of Botany,Bulgarian Academy of Sciences,Sofia,Bulgaria |
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Abstract: | 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. |
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