Ploidy level variation in the genus Rubus in the Pannonian Basin and the northern Balkans, and evolutionary implications

Ploidy can serve as an excellent diagnostic character and proxy for evolutionary and reproductive behaviour, particularly in taxonomically complicated apomictic genera. In Rubus, ploidy level has so far been established for 230 European species (ca 30% of the total), mainly from Western or central Europe. We present the first DNA ploidy data for 25 described species and 22 undescribed stable morphotypes from the Pannonian Basin and the northern Balkans (8 countries). We also review previously published ploidy data covering the entire bramble flora of the studied area (78 recognized species in total). The most common ploidy level is tetraploid, which is the only ploidy level in most series (e.g. Micantes, Rhamnifolii, Sylvatici). This likely reflects elevated sexuality and the higher probability of new species formation via hybridization in tetraploids compared to other ploidy levels. As in central Europe but unlike in other regions, we also recorded many triploid species, namely in ser. Discolores (19 species) and ser. Rubus (four species). The diversity of triploid Discolores in the region may be linked to the occurrence of diploid R. canescens, making the region a hot spot of triploid Rubus diversity. Six pentaploid and a single hexaploid species, all from sect. Corylifolii, were recorded. Ploidy proved to be a good diagnostic character for several species that are difficult to distinguish morphologically, confirming its importance in inventories of brambles. One of these species is described here as R. praecocifrons Király & Trávn.