RAPD analysis points to old world Bromus species as ancestral to new world subgen. Festucaria

The genus Bromus subgen. Festucaria is a widespread Old World and New World taxon having genomes A, B and L, distinguished cytogenetically. Stebbins (1981) suggested that evolution in Bromus went from the small genomes A and B to the large genome L. Thus, Old World species with genomes A and B could be ancestral to New World species with genome L. To test this hypothesis we carried out RAPD analysis of a representative group of species from subgen. Festucaria. RAPD band patterns enabled resolution of 13 species after excluding the species-specific bands with high/moderate support. The basal position of Bromus variegatus M. Bieb. - an Old World species presumably having a B genome - in relation to some New World species with the genome L confirmed Stebbins' hypothesis of its ancestry in relation to the Old World species. The group of high bootstrap support, B. cappadocicus Boiss. et Balansa-B. erectus Huds.-B. riparius Rehm., with genome A. and a distinctly xerothermic ecological profile, was related to a New World species with genome L, B. auleticus Trin. ex Nees, pointing to their presumably common evolutionary history.