Ruins of medieval castles as refuges for endangered species of molluscs

Molluscan communities were studied at 114 castles in the Czech Republic. Altogether 70% of the land fauna species of the Czech Republic were found at these sites. A range of environmental factors were recorded at each, and analysed for their influence on species diversity. The variability of the molluscan communities was assessed. It was shown that castles act as islands (positive effect of castle size on species number) and that a high degree of castle disintegration negatively affected species diversity. Limestone as a rock substrate was found to be a very important factor, while the effect of calcium in tree litter was unimportant. Species indicative of some environmental variables were identified. A complete literature review on castle-related molluscan fauna was performed for the Czech Republic. Castles present a characteristic set of habitats markedly differing from the surrounding landscape. Thus, they represent significant refuges for many species, as indicated by the high species diversity and the presence of rare and geographically isolated species.