Interactions between Galba truncatula (Gastropoda, Lymnaeidae) and two land snail species on the acid soils of central France

Abstract

ABSTRACT Interactions between Galba truncatula and two species of land snails (Cochlicopa lubrica, Succinea putris) that colonise lymnaeid habitats in June-July were studied by introducing G. truncatula into new sites (Experiment A) or removing it from its natural habitats (Experiment B). Snail counts were performed in late May or early June for the eight years following introduction or removal of G. truncatula. The results were compared to those observed at control sites where G. truncatula was absent. In sites where G. truncatula was introduced (Experiment A), the mean density of the lymnaeid peaked in the second year and gradually decreased in subsequent years. Conversely, the mean density of the land snails decreased sharply in the second year before increasing rapidly for S. putris and gradually for C. lubrica in subsequent years. Removal of G. truncatula from its natural habitats (Experiment B) had no significant effect on the mean density of C. lubrica. In contrast, that of S. putris peaked in the second year and decreased rapidly to lower values in subsequent years. Density interactions between G. truncatula and the two land snail species indicate that there is probably competition between these species for space in lymnaeid habitats in May and June.