Distribution of habitat specialists in semi-natural grasslands

Questions: To what extent do semi-natural grasslands differ in community specificity (i.e. the representation of habitat specialists in a community)? Does the community specificity coincide with evolutionary history and nutrient availability of the habitats? Location: West Carpathian semi-natural grasslands (Czech Republic, Slovakia, Poland). Methods: Habitat specificity of individual plant species was derived from species co-occurrence patterns using the Czech and Slovak vegetation databases (48 240 non-forest vegetation plots). The vegetation data set, i.e. semi-natural grasslands in West Carpathians, was classified into different plant communities using modified twinspan. The communities were split according to geographic position, in either Outer or Inner West Carpathians, and analysed separately. Values of community specificity for particular plant communities were compared with expectations generated by null models. The species habitat specificity was correlated to species Ellenberg indicator values for nutrients. Results: Several plant communities have higher representation of habitat specialists than expected by chance, mainly semi-dry grasslands in the Outer West Carpathians, and calcareous fens and higher-altitude meadows in the Inner West Carpathians. Habitats that have occurred in the region since the early postglacial period are rich in habitat-specialized grassland species. Habitat specialists tend to occur in nutrient-poor habitats and generalists in nutrient-rich habitats. Nevertheless, some communities on productive habitats and with a relatively short history also show high level of community specificity. Conclusions: Community specificity can be a useful parameter to describe the origin and determinants of semi-natural grassland biodiversity. Although the habitat persistence at the Holocene scale and nutrient availability are important factors underlying specialist occurrence, their distribution is probably also controlled by a complex set of interacting factors including, e.g. recent management practices.