Consequences of the pollination system on genetic structure and patterns of species distribution in the Andean genus Polylepis (Rosaceae): a comparative study

As a member of the Sanguisorbinae, taxonomically complicated Polylepis Ruiz & Pav. from the South American Andes is one of the few wind-pollinated genera of Rosaceae. Here, it is suggested that problems traditionally faced in species delimitation and phylogeny reconstruction may be in part due to a combination of weak reproductive barriers and the large distances that can be covered by genetic information as a result of wind pollination. The pattern of species distribution as well as molecular data (AFLP) of Polylepis were contrasted with those of an unrelated, insect-pollinated genus of similar species number and distribution, Minthostachys (Griseb.) Spach (Lamiaceae). In the present case, extensive pollen-mediated gene flow may explain the homogenization of genetic variability over larger distances and a lower number of species restricted to individual countries in the wind-pollinated genus Polylepis, but more examples will have to be studied before arriving at final conclusions.