Ploidy levels and their relationships with the rainfall in several populations of Patagonian species of Berberis L.

The ploidy levels and pollen staining of 68 populations belonging to 13 spe cies of the genus Berberis L., growing in the Argentinian Patagonia under d ifferent environmental conditions, were analyzed as a part of a multidiscip linary study to obtain information about the evolutionary history of the ge nus. The chromosome number of Berberis bidentata, B. cabrerae, B. chillanen sis, B. darwinii, B. empetrifolia, B. ilicifolia, B, linearfolia, B. microp hylla, B. montana, B. parodii and B. serrato-dentata is 2n = 28, whereas B. buxifolia and B. heterophylla have 2n = 56. The relationship between ploid y levels and rainfall showed that, contrarily to the species with 2n = 28, B. buxifolia and B. heterophylla (2n = 56) grow in areas where the rainfall range is low. The opening of new habitats for colonization as a result of climatic change provides an ecological opportunity for the polyploids to ex ploit their inherent advantage.