Reopening an old chapter: a revised taxonomic and evolutionary concept of the Rubus montanus group

The triploid complex of Rubus montanus (Rubus ser. Discolores, Rosaceae) is a particularly intricate group due to its plasticity and variability. The representatives of this group are, notwithstanding the high number of taxon names published, often considered a single species (Rubus montanus s.l.). In the course of extensive field studies and herbarium revisions we revealed three widely distributed morphologically defined types that were formerly incorporated in R. montanus s.l. but should be treated as separate species. We analysed them using both morphological and genetic methods. We found that the species examined are identical with the formerly described R. montanus Lib. ex Lej., R. bicolor Opiz and R. velutinus Vest ex Tratt., and provide a taxonomic reassessment, discussion of synonymy and typification of certain taxon names, and complete their morphological description, ecological characteristics and distribution. We show that the morphological delimitation of the triploid Discolores microspecies is highly compatible with molecular evidence for the independent sexual origin of these units (or, rarely, extensive mutational diversification). On the contrary, the intraspecific genetic variation is rather low and only mutational, and confirms their strictly apomictic reproduction. Nevertheless, mutational load may be substantial and mutation-based and recombination-based variation overlap in some instances. Highly variable molecular genetic markers such as microsatellites are recommended as an additional line of evidence for species delimitation in any further taxonomical studies on other groups of brambles.