The structure of allozyme variation in Silene nutans (Caryophyllaceae) in Denmark and in north-western Europe

We used allozymes to investigate the structure of genetic variation in populations of the perennial herb Silene nutans at local (Denmark), regional (Nordic area) and wide (over a 19A degrees latitudinal gradient) geographic scales in north-western Europe. New data from Denmark were combined with data from previously studied Fennoscandian and western populations. We related patterns of nuclear variation for 26 Fennoscandian and western populations to the phylogeographic patterns revealed by four plastid (chloroplast) DNA markers. Levels of genetic diversity were similar within Denmark and Sweden/N Finland. Compared to Sweden/N Finland, the Danish populations show lower and nonsignificant F (IS) values. The genetic structure reveals no grouping of the Danish populations according to their geographic origin (Jutland-Zealand). Within Nordic populations (from Denmark, Sweden and N Finland), there is a weak geographic pattern of allozyme differentiation. The high latitude populations are genetically depauperate compared with populations from Western Europe. At the whole north-western European scale, the structure of allozyme variation within S. nutans shows geographic differentiation (Nordic versus western populations), and some congruence with plastid phylogeographic patterns. A high level of allozyme genetic differentiation is found between Nordic and western populations (8.0 %), but also between populations within haplotype categories (19.4 %). The overall geographic structure of allozyme variation of S. nutans appears to be primarily a reflection of past (postglacial) migration history, whereas more recent adaptive and stochastic processes have occurred at more local scales.