Two distinct AFLP types in three populations of marram grass (Ammophila arenaria) in Wales

The genetic structure of marram grass populations at coastal and inland locations, 200 m apart, was investigated at three sites by means of amplified fragment length polymorphism (AFLP) DNA markers. We expected a genetic differentiation between coastal and inland populations and more genetic variation in the coastal areas as a result of different events of colonization by different plant materials. An assignment test showed that the sampled Ammophila arenaria could be assigned to two groups based on AFLP data. The spatial distribution of the two AFLP types of A. arenaria varied with sampling location. In two of the three locations, mainly one type (1) was found in the newly formed dunes. This type did also occur further landward, but the second type (2) was preferentially found in inland populations. Genetic diversity was very low and of similar value in both coastal and inland populations. For each site, outlier loci with respect to FST value were identified, which may be indicative of different selection pressures in coastal compared with inland clusters. However, no identical outlier loci were found at all three sites. Possible explanations for the observed difference in distribution of type 1 and 2 populations between coastal and inland sites are discussed