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

Genetic diversity has been investigated by the application of molecular mar kers in, for the first. time, all the taxa recognised in recent treatises o f the genus Hippophae. RAPD (random amplified polymorphic DNA) analyses wer e 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 th ese markers were useful for analysis of interspecific relationships, wherea s others can be considered as taxon-specific markers. Clustering of taxa an d populations in our neighbour-joining based dendrogram was in good agreeme nt with some recently suggested taxonomic treatises of Hippophae. Amount an d distribution of genetic variability varied considerably between species. Partitioning of molecular variance within H. rhamnoides supported earlier f indings that a considerable part of the total variance resides among subspe cies (59.6%). Within-population variability also differed considerably. Per centage polymorphic RAPD loci and Lynch and Milligan within-population gene diversity estimates showed relatively high values for some species close t o the geographic centre of origin in Central Asia, e.g. H. tibetana and the putatively hybridogenous H. goniocarpa. Spatial autocorrelation analyses p erformed on 12 populations of H. rhamnoides revealed positive autocorrelati on of allele frequencies when geographic distances ranged from 0 to 700 km, and no or negative autocorrelation at higher distances. At distances betwe en 700 and 1900 km, we observed deviations from the expected values with st rongly negative autocorrelation of allele frequencies. A corresponding rela tionship between geographic and genetic distances could not be found when t he analysis instead was based on one population from each of 8 species.