Chloroplast DNA variation in the European herb Silene dioica (red campion): postglacial migration and interspecific introgression

Many recent studies of intraspecific geographic variation in maternally inherited chloroplast DNA (cpDNA) in European trees have revealed haplotype distributions that can be interpreted in terms of scenarios of postglacial migration and range expansion. However, there is still a lack of comparable information from widespread herb species. In the present study, we investigated the geographic distribution of cpDNA variation in 124 populations, covering a large part of the range of the widespread, dioecious, European herb, Silene dioica. PCR-RFLP analysis revealed 24 different cpDNA haplotypes. As in the majority of European tree species, the large-scale geographic distributions of the most common S. dioica haplotypes suggest that the species colonized Europe from more than one geographic source. Material from 16 populations of S. latifolia and five hybrid populations was also included in the study for comparative purposes. Five out of seven haplotypes detected in S. latifolia were shared with S. dioica. The similarity of the geographic distributions of the shared haplotypes in both species is consistent with a history of past and/or recent interspecific hybridization and introgression between these closely related plants. The two haplotypes detected only in S. latifolia were present in populations in the Mediterranean region – on the southern margin of the species’ area of sympatry, or outside the range of S. dioica.