Cytological, genetic and morphological variation in mixed stands of dogroses (Rosa section Caninae; Rosaceae) in Germany with a focus on the hybridogenic R. micrantha

Abstract

Polyploid, hemisexual dogroses are known for their complicated reticulate evolutionary history and their ongoing hybridization events that challenge taxonomic concepts. We investigated how spontaneous hybrids between subsections Rubigineae and Caninae can be identified by cytological, genetic and morphological analyses and how they fit into the current taxonomic treatment. We sampled plants from mixed stands of both subsections in Germany and performed morphological measurements. We compared the morphological data with data from flow cytometry and microsatellite analyses compiled from a previous study based on a much wider sampling. Most of the investigated plants were pentaploid, but some species were composed of tetra- and hexaploid individuals co-occurring with the pentaploids. In Germany, all hexaploid plants were of hybridogenic origin and they were more frequently found in south-western Germany. Genetic and morphological data differentiated clearly between subsections and between informal aggregates of subsection Rubigineae. However, the currently accepted microspecies could be neither genetically nor morphologically unambiguously recognized. In contrast, multivariate analyses of genetic and morphological data distinguished between hexaploid and pentaploid cytotypes of the R. rubiginosa aggregate. The hexaploid hybridogenic individuals, mostly identified as R. micrantha, were characterized by more hairs and fewer glands on the leaflets and a smaller angle of the lamina base, characters typical for the paternal parent of subsection Caninae.