Genotypic structure in clonal Rhododendron ferrugineum L. (Ericaceae) populations: origin and maintenance

Genotypic structure of a closed population of the clonal ericaceous shrub Rhododendron ferrugineum is examined in the light of two independent studies previously conducted on this species. In the first study, spatial distribution of genotypes in the closed population was inferred from the amplified fragment length polymorphism (AFLP) procedure. Age of clones was estimated using their spatial extent and the annual growth rate of shoots. In the second study, ramet demography was studied in the three most representative stages of shrub invasion on two different sites, including the site where the population investigated by AFLP grew. The demographic data recorded were the area occupied by ramets and ramet age, and from this information the developmental pattern of Rhododendron populations was determined. Additional data such as genet density and distance between genets were calculated.These two sources of information allow us to propose that all or most of the clones detected in the closed population established at the early successional stage, and that the present genotypic structure was established several hundred years ago, long before the population reached total closure. Hypotheses concerning the future development of this genotypic structure are discussed.