RESTRICTED GENE FLOW AND SUBPOPULATION DIFFERENTIATION IN SILENE DIOICA

The size of breeding units and the hierarchical population structure o f the dioecious perennial herb Silene dioica were investigated on four closely situated island populations in the Skeppsvik Archipelago in n orthern Sweden. F-statistics analyses of nine polymorphic allozyme loc i revealed that plants on single islands are divided into many small b reeding units, between 0.2 m(2) and 6 m(2). Hierarchical analyses show ed that levels of differentiation among subpopulations within islands (F-PL = 0.080) were about twice as high as among islands (F-LT = 0.048 ). These results are discussed in the light of what is known about pol len and seed movement in the archipelago.