Allozyme diversity in slugs of the Carinarion complex (Mollusca, Pulmonata)

Abstract

Previous allozyme analyses of the hermaphroditic terrestrial slugs Arion fasciatus, A. circumscriptus and A. silvaticus (subgenus Carinarion) have suggested that in North America these species are each single monomorphic strains. However, new data on 18 putative enzyme loci show that in western Europe the three taxa, respectively, consist of at least three, two and 12 homozygous multilocus genotypes (strains), which regularly co-occur. The current opinion that American and European Carinarion populations are similarly structured, and that colonization events did not affect the population genetics of North American Carinarion, should therefore be readdressed. The present data also provide the first indication of heterozygosity and possible outcrossing in Carinarion. Nevertheless, uniparental reproduction is confirmed as the main breeding system in West European Carinarion, although the high incidence of multistrain populations in A. silvaticus and A. fasciatus appears at variance with the current model of population genetic structuring in selfing terrestrial pulmonates. Finally, the systematic status of the three Carinarion spp. is tentatively questioned.