MOLECULAR DIVERSITY AND DERIVATIONS OF POPULATIONS OF SILENE-ACAULIS AND SAXIFRAGA-OPPOSITIFOLIA FROM THE HIGH ARCTIC AND MORE SOUTHERLY LATITUDES

A survey of allozyme diversity within and between populations of Silen e acaulis from Spitsbergen, Norway, Iceland and Scotland, showed that populations from the high Arctic (Spitsbergen, > 76 degrees N) contain ed high levels of diversity and were genetically similar to population s from more southern locations. Indirect measures of gene flow (Nm), c alculated from Wright's F-st, indicated that there had been extensive gene flow between Spitsbergen and some Norwegian populations. A restri ction site analysis of chloroplast DNA (cpDNA) in S. acaulis revealed that all populations contained a single identical cpDNA haplotype, exc ept one population from Norway which also contained a second haplotype . In contrast, five different cpDNA haplotypes were distinguished in a more limited survey of cpDNA variation in Saxifraga oppositifolia, wi th all five haplotypes present in one of two Spitsbergen populations s urveyed. The contrasting cpDNA results for the two species suggest tha t whereas high-Arctic populations of Silene acaulis have most likely b een derived from immigrants which arrived from the south after the las t glacial period, high-Arctic populations of Saxifraga oppositifolia m ay be derived, in part, from ancient northern stocks which survived th e last glaciation in high-Arctic refugia.