Our long-term palaeoecological research on plant and mollusc assemblages in more than 170 isolated fen sites in the Western Carpathians proved a sharp gradient of species turnover spans from west to east, mainly in the distribution of so-called re - lict species, independent of any ecological difference among sites. Fossil evidence and radiocarbon dating evidenced that sites in the outer flysch part (e.g. border area between the Czech and the Slovak Republics) are much younger than those located in the Inner Western Carpathians, host many relict species and have a Holocene continuity. We also confirmed that se - veral presumable relict species are signifi - cantly related to old sites originating from the Pleistocene/Holocene boundary. and Michal Horsák a kol.