Low genetic and morphological differentiation in the European species complex ofRosa sherardii,R. mollisandR. villosa(RosasectionCaninaesubsectionVestitae)

Abstract

The polyploid species complex of Rosa villosa sensu lato (Rosa section Caninae subsection Vestitae) consists of three morphologically similar polyploid species: R. sherardii, R. mollis and R. villosa. Whereas R. sherardii is distributed in central Europe, R. mollis and R. villosa represent a vicariant species pair occurring in northern Europe and in mountains of central and eastern Europe, respectively. In this study we analysed multiple data sets (morphology, cytology, microsatellites, AFLP and plastid DNA sequences) to re-evaluate the systematics of these species and to examine whether cytological differences are reflected in the taxonomy and geographical distributions. Furthermore, these data sets were used to evaluate hypotheses explaining the vicariant distribution of R. mollis and R. villosa. None of these data sets revealed a clear-cut differentiation between the species. Cytological and molecular data argued for a discrete taxonomic position of the predominantly pentaploid R. sherardii, but these data did not support a separation between the mostly tetraploid R. mollis and R. villosa. Population genetics revealed that samples of the latter species were assembled according to ploidy, but not to species affiliation or geographical distribution. Thus, we assume that the cytologically polymorphic original species had a continuous range prior to the last glaciation period and survived on nunataks or in non-glaciated coastal regions in northern Europe, but that it failed to recover its former range after the retreat of the ice sheets. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 174, 240–256.