Nivní malakofauna eky Oh e – její minulost a sou asnost The floodplain molluscan fauna of the Oh e River (Czech Republic) – its past and present

The recent molluscan assemblages of all floodplain forests on the 256 km long Oh e River were studied (West and Northwest Bohemia, Czech Republic). Altogether, 75 species of terrestrial Gastropoda representing 30% of the total Czech malacofauna, were recorded at sites selected during previous and recent research from 1950 2010. The Oh e malacofauna is impoverished of many forest and floodplain species in comparison to molluscan assemblages of smaller Bohemian rivers to the west and northwest. The richest molluscan assemblages occur on the upper part of the river, while the middle and lower parts are very poor. Low alpha-diversity of these parts of the Oh e River can be explained by (1) intensive agriculture in floodplain areas of the middle part of the river, (2) the migration barrier of the Nechranice Dam between the upper and middle river parts, and (3) long-term human influence on the lower part of the Oh e River during the Holocene.