KNOTT, K.E.*; PUURTINEN, M.; KAITALA, V.; University of Jyv�skyl�, Finland; University of Jyv�skyl�, Finland; University of Jyv�skyl�, Finland: Mating systems in populations of the hermaphroditic snail Lymnaea stagnalis

The aquatic snail Lymnaea stagnalis is a simultaneous hermaphrodite capable of both self and cross fertilization. In order to determine the mating system in natural populations of this species, we have studied microsatellite variation in eight populations of Lymnaea stagnalis from lake habitats in central Finland. For each population, we examined variation of nine microsatellite loci in both adult and juvenile cohorts and used Ritland�s population genetics approach to measuring inbreeding depression in the wild (K. Ritland 1990 Evolution 44(5):1230-1241). Inbreeding depression was also calculated from a laboratory-based mating experiment. Estimates for inbreeding depression determined from these two different methodologies were compared. With this information, we hope to further understand the role of inbreeding depression in the evolution of mating systems in Lymnaea stagnalis and possibly other hermaphroditic animals. We found that the microsatellite loci identified here had only low to moderate levels of polymorphism (each with 2 to 7 alleles), which may be indicative of a predominately selfing species. However, microsatellite variation was quite different among populations, with two populations being essentially monomorphic at all loci and other populations with moderate or relatively high levels of heterozygosity.