Variation in Desiccation Tolerance in Freshwater Snails and Its Consequences for Invasion Ability

Abstract

The freshwaters of Martinique (French West Indies) have recently been invaded by snails belonging to the Thiaridae family (Gastropoda; Prosobranchia). Eight distinct Thiarid lines have been successively introduced in Martinique, and are still in the process of sequentially replacing one another within local habitats, revealing a range of increasing invasive abilities. Our aim was to test whether the variation in invasive ability can be partly explained by a specific life-history trait, desiccation tolerance, which might be important in view of the typical instability of tropical freshwater habitats. We therefore tested desiccation tolerance in both juveniles and adults under laboratory conditions. Our data show that, although all Thiarid lines resist desiccation quite well, they exhibit extreme variation in the degree of tolerance. These differences are mostly mediated by individual size, but are definitely of genetic origin given that our individuals were of similar ages and were raised under standardized laboratory conditions. The overall invasive success of a line in Martinique, deduced from field surveys, does not correlate with its desiccation tolerance. However, desiccation tolerance does seem to be a limiting factor for the invasion of the small fraction of habitats that are most exposed to drought. More generally, our study exemplifies the possibility that the invasion differential among habitats, rather than a general invasion ability, be predicted according to a particular life-history trait, within a set of closely related invasive taxa.