Ecogeography of the grass genusHelictotrichon (Poaceae: Aveneae) in the Mediterranean and adjacent regions

Abstract

The geographical distribution of the grass genusHelictotrichon in the Mediterranean Region is analysed and mapped for 33 taxa. Based on only a single life form (perennial herb), a variety of edaphically, climatically and altitudinally differently adapted species complexes has evolved in the area. Most of these complexes show west-east disjunctions and contain geographically, sometimes even edaphically vicarious taxa with complementary distribution. A transition from mesomorphic to xeromorphic habit occurred independently in different species groups and led to the establishment of the “modern” Mediterranean taxa which are in part highly polyploid derivatives of more mesophilic diploids. The significance of polyploidy, patterns of parapatric and sympatric distribution, biogeographical borders, and centres of species diversity are discussed in context with the history of the Mediterranean vegetation. New combinations are:Helictotrichon setaceum subsp.petzense, H. pratense subsp.lusitanicum, H. praetutianum.