Inter- and intraspecific genetic variation in Hippophae (Elaeagnaceae) investigated by RAPD markers

Genetic diversity has been investigated by the application of molecular markers in, for the first. time, all the taxa recognised in recent treatises of the genus Hippophae. RAPD (random amplified polymorphic DNA) analyses were conducted with 9 decamer primers, which together yielded 219 polymorphic markers. We found 16 fixed RAPD markers, i.e. markers that either occurred in all plants of a population or were absent from all plants. Several of these markers were useful for analysis of interspecific relationships, whereas others can be considered as taxon-specific markers. Clustering of taxa and populations in our neighbour-joining based dendrogram was in good agreement with some recently suggested taxonomic treatises of Hippophae. Amount and distribution of genetic variability varied considerably between species. Partitioning of molecular variance within H. rhamnoides supported earlier findings that a considerable part of the total variance resides among subspecies (59.6%). Within-population variability also differed considerably. Percentage polymorphic RAPD loci and Lynch and Milligan within-population gene diversity estimates showed relatively high values for some species close to the geographic centre of origin in Central Asia, e.g. H. tibetana and the putatively hybridogenous H. goniocarpa. Spatial autocorrelation analyses performed on 12 populations of H. rhamnoides revealed positive autocorrelation of allele frequencies when geographic distances ranged from 0 to 700 km, and no or negative autocorrelation at higher distances. At distances between 700 and 1900 km, we observed deviations from the expected values with strongly negative autocorrelation of allele frequencies. A corresponding relationship between geographic and genetic distances could not be found when the analysis instead was based on one population from each of 8 species