Mosaic variation in allozyme and plastid DNA markers in the European ranges of Silene vulgaris and its partially sympatric relative S. uniflora (Caryophyllaceae).
The perennial herbs Silene vulgaris and S. uniflora are closely related, partially sympatric and interfertile, yet morphologically distinct. We used nuclear (allozyme) and plastid (polymerase chain reaction-restriction fragment length polymorphism) DNA markers to investigate whether these species have a shared history of postglacial colonization and hybridization in Europe, as inferred from large-scale patterns of geographic variation. The majority of plastid haplotypes and allozyme alleles were widespread and patchily distributed within both species and there was no geographic structure in the distributions of shared allozymes or haplotypes. The mosaic variation is consistent with a scenario in which repeated episodes of interspecific hybridization pre-dated the largely allopatric range expansion of the two species during the postglacial period. Our overall results are not consistent with a scenario of extensive hybridization and introgression during the postglacial range expansion of the species or within their current areas of sympatry, but we found some evidence for local, postglacial evolution and hybridization in the Baltic region.