Ancient Origin of Two 5S rDNA Families Dominating in the Genus and Their Behavior in the Canina-Type Meiosis.

The genus comprises more than 100 woody species characterized by intensive hybridization, introgression, and an overall complex evolutionary history. Besides many diploid species (2n = 2x = 14) polyploids ranging from 3x to 10x are frequently found. Here we analyzed 5S ribosomal DNA in 19 species covering two subgenera and the major sections within subg.