HABITAT-RELATED DISPERSAL IN THE ROCK-DWELLING LAND SNAIL CHONDRINA-CLIENTA

Habitat type may influence dispersal in a variety of animal species. We examined dispersal in the rock-dwelling land snail Chondrina clienta in a limestone pavement, on vertical rock walls, a pile of stones and a stone wall on the Baltic island of Oland, Sweden. Dispersal was estimated by recording movements of marked C. clienta in natural populations over 3 yr. Dispersal differed significantly between habitat types. The largest distances dispersed were recorded in the limestone pavement (264 cm yr(-1); median distance) and on vertical rock walls (96 cm yr(-1)), simple habitats for travelling snails. Dispersal was less in the stone pile (68 cm yr(-1)) and on the stone wall (88 cm yr(-1)) that are more complex habitats with multiple layers of pieces of stones. Distances dispersed also varied among vertical rock walls, indicating that other factors such as exposure of the rock surface and size of the habitat may be important in determining snail dispersal. The results of two experiments indicated that grassland vegetation may inhibit dispersal in C. clienta, and that isolated stones covered with lichens might serve as stepping stones for dispersing snails in otherwise unsuitable grassland. Snail size (age) influenced distances moved, but might only be important in determining daily movements,not dispersal over longer periods. Dispersal in C. clienta is habitat specific and cannot be characterized by a single parameter.