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The occurrence of inbreeding was investigated in Celleporella hyalina, which has been reported as being capable of selfing. In total, 4 tetranucleotide microsatellite markers were scored In populations from sites within the Menai Strait (Wales) and the Yealm Estuary (Plymouth, England). All loci in all populat~ons were in Hardy-Weinberg equilibrium, with insignificant F,, values, which indicates that C. hyalina in these populations generally outbreed. No significant differences were found between populations up to 8 km apart, indicating sufficient gene flow on this scale to form a single breeding population despite geographic separation. The Plymouth population was significantly (p < 0.00001) deviant from the others, indicating possible isolation by distance at the scale of 900 km. C. hyaLina cultured in the laboratory were observed to spawn sperm into the surrounding seawater. Sib larvae were found to settle randomly with respect to each other. In isolation C. hyalina failed to produce offspring, though a small proportion brooded abortive embryos. Pairings between individuals of differing genotypes resulted in the production of offspring, all of which, when genotyped with respect to the parent colonies, were found to be the result of outcrossing.

Quantitative descriptions of population genetic structure allows the delineation of population units and is therefore of primary importance in population management and wildlife conservation. Yet, predicting factors that influence the gene flow patterns in populations particularly at landscape scales remains a major challenge in evolutionary biology. Here we report a population genetic study of the common dormouse, Muscardinus avellanarius, a species that is seriously threatened due to anthropogenic factors, in two regions, Bontuchel (Denbighshire) and Afonwen (Gwynedd), both in Wales, UK. Ten microsatellite loci were used to characterize patterns of genetic diversity of M. avellanarius within both regions. While the population differentiation between both regions is apparent through geographical scale separating them, by using Bayesian clustering analyses, we identified the occurrence of genetic division among populations of M. avellanarius in Bontuchel region, but no significant evidence of differentiation in Afonwen. We found a strong significant isolation-by-distance (IBD) pattern at a fine-scale (less than 1 km) within continuous habitat and between habitat patches in both regions. Overall, analyses suggest that small-scale dispersal associated with the social structure and dispersal tendencies of this species is reflected in the genetic structure of populations. These findings then provide useful baseline data for supporting local management strategies.