• biogeography;
  • Hordeum (Poaceae;
  • Triticeae);
  • long-distance dispersal;
  • phylogeny;
  • vicariance


  • • 
    The grass genus Hordeum (Poaceae, Triticeae), comprising 31 species distributed in temperate and dry regions of the world, was analysed to determine the relative contributions of vicariance and long-distance dispersal to the extant distribution pattern of the genus.
  • • 
    Sequences from three nuclear regions (DMC1, EF-G and ITS) were combined and analysed phylogenetically for all diploid (20 species) and two tetraploid Hordeum species and the outgroup Psathyrostachys. Ages of clades within Hordeum were estimated using a penalized likelihood analysis of sequence divergence.
  • • 
    The sequence data resulted in an almost fully resolved phylogenetic tree that allowed the reconstruction of intrageneric migration routes. Hordeum evolved c. 12 million years ago in South-west Asia and spread into Europe and Central Asia. The colonization of the New World and South Africa involved at least six intercontinental exchanges during the last 4 million years (twice Eurasia–North America, North America–South America, twice South America–North America and Europe–South Africa).
  • • 
    Repeated long-distance dispersal between the northern and southern hemisphere were important colonization mechanisms in Hordeum.