Rhododendron ferrugineum L. (Ericaceae) is a subapline shrub found throughout the Pyrenees and Alps, usually at elevations of 1600 – 2200 m. We used 115 dominant AFLP markers to assess genetic structure over wide spatial scales, to gain insights into the relationships between genetic and geographic distance. Leaf tissue was sampled from 10 plants from each of 17 sites across the species’ range, with the maximum distance between sites of over 1000km. In addition, at two of the sites we used transects to sample at distances ranging from 10m to 3000m. We found no distinct patterns in terms of the distribution of polymorphic loci, so that it is not yet possible to distinguish recently-colonized sites based on the effects of genetic drift. We observed a positive relationship between genetic distance and spatial distance at the small scales (10 – 1000m), but this breaks down at greater geographic distances. However, there is considerable variation among loci: at some loci, the dominant allele has a restricted geographic range, whereas alleles at other loci are distributed more continuously over the range. Overall patterns of genetic variation are consistent with rapid postglacial colonization as well as high levels of gene flow among sites.

Key words: AFLP, genetic distance, isolation by distance, Rhododendron ferrugineum