Ecological and historical determinants of Western Carpathian populations of Pupilla alpicola (Charpentier, 1837) in relation to its present range and conservation

The minute snail Pupilla alpicola (Stylommatophora: Pupillidae)is known as a threatened glacial relict restricted to treelesscalcareous fens with Holocene continuity, mainly in the Alpineand Carpathian regions. We summarize all available data on thedistribution of P. alpicola and analyse its ecologicalrequirements in the Western Carpathians both at a larger,regional scale (162 sites) and at a smaller, within-site scale(10 sites). Viable populations of Pupilla alpicola occurred in31 sites out of the 162 fens studied. Water conductivity,Ellenberg’s indicator values for soil reaction, light andnutrients were the main ecological variables that explainedthese occurrences. The species preferred sites with extremelyhigh calcium carbonate precipitation, low nutrients and sparseherb vegetation cover. Its present distribution in the WesternCarpathians is strongly related to a spatial–temporal continuumof calcareous fens throughout the Holocene; none of the modernpopulations was located further than 40 km from the knownpalaeorefugium. Direct fossil evidence shows that thesepalaeorefugial fens have persisted since thePleistocene/Holocene transition. A conservation strategy forthis rare species needs to take account of both historicalcontinuity and the maintenance of appropriate ecologicalconditions.