Is the mollusc Ena montana (Draparnaud, 1801) invasive or relict speciesin Lithuania?

Abstract: Usually invasive molluscs represent some of the world’s most important ecologicaland economic pests which quickly and abundantly colonize habitats not typical for theirprovenance. In this sense E. montana is local in the mountains of Alps, Carpathians, Sudetenunder 2800 m but in Lithuania it was found in the Northern Lithuanian Lowland. The firstfinding of E. montana in Lithuania was made in 1958 by P. Šivickis and our data show that thisspecies is abundant in Biržai forest (maximum 314 individuals in one square meter). Converselywe can assert that E. montana is post-glacial relict species of the Holocene because itsdistribution in Lithuania have the most striking feature – it was found only in one location – inone of the oldest woodland of Lithuania – Biržai forest. Regrettably we don‘t have fossil datafrom this part of Lithuania and the implication above was made only after intensive molluscssearch in 238 localities of Lithuania during the Woodland Key Habitat Inventory in 2001-2005.The differences in gleysols between other woodland sites in Lithuania are fractionally except fortwice bigger Mg2+ ions (30 mg/kg) and high humidity in Biržai forest. During the past fewdecades Biržai forest was intensively exploited and melioration took place since 1960 till 2004.Since all known places for E. montana are in the most humid central part of Biržai forest, whatprognosis can we make – will E. montana spread or decrease? The other question is, can weassociate this population with one from Latvia Gauja National park which is known for theDevonian sandstone cliffs, in some places reaching 90 meters, along the banks of the Gauja river,or mountains of Poland, where the nearest populations of E. montana can be found? All thesequestions are under discussions.