Ecogenetic Comparison of the Selfing Terrestrial Slugs Arion Silvaticus and A. Circumscriptus in Belgium (Mollusca: Pulmonata: Arionidae)

摘要

The distribution of the predominantly selfing terrestrial slugs Arion silvaticus and A. circumscriptus was compared in ten habitat types in Belgium. The two species occurred in respectively nine and five of these habitat types. A comparative allozyme analysis revealed that A. silvaticus was genetically more variable than A. circumscriptus, since 15 homozygous multilocus genotypes (strains) were found in A. silvaticus, while A. circumscriptus only involved two strains. We tentatively argue that this result, combined with the wider habitat range of A. silvaticus fits into Van Valen's niche-width variation hypothesis and is the first demonstration of a positive relation between ecological and genetic variability (i.e. strain diversity) in autogamous pulmonates. Pastures and fir-woods are the most diverse habitat types in terms of strain composition. In many populations several of these strains co-occurred. This seems at variance with many other (mainly) self-fertilizing multistrain species, the local populations of which consist of single strains. There was a high niche-overlap (no ecological differentiation) between strains for which enough data were available.