Polyploidy and hybridization in Bulgarian Brassicaceae: distribution and evolutionary role

The results from the investigation and analysis of the chromosome numbers and ploidy levels of 141 species and not nominal subspecies of Brassicaceae, their distribution and phytogeographical relations are discussed. Nearly 65 % of the taxa are diploids, most of them perennials, Mediterranean, Anatolian and Pontic floristic elements. Another 35 % are polyploids, c. 2/3 of them with tetraploid cytotypes. The rest of the polyploids have chromosome numbers ranging from hexato dodecaploid level. The polyploid cytotypes in Erysimum, Rorippa, Cardamine, Alyssum, and Iberis, occurring mostly in the Rilo-Rhodope Massif, are discussed in the light of the position of these mountains in a transitional climatic zone between continental European and Mediterranean climates, as well as of the role of the Quaternary climatic changes for stimulation of the hybridogenesis and species differentiation in the Southern Balkans, one of the major glacial refugia in South Europe.