Analysis of hybridization between Grindelia brachystephana and G-chiloensis (Asteraceae : Astereae) in Patagonia, Argentina

Intermediates between two South American species of Grindelia were found in Chubut Province, Argentina. Twenty eight individual plants with phenotypes of G. brachystephana, G. chiloensis, or intermediates were collected and s tudied together with three reference specimens of each of the putative pare ntal species. Discriminant analysis procedure and the computer program HYWI N were applied and results of the two methods are compared. Results demonst rate that most of the specimens collected are of hybrid origin, and that mo st of the specimens suggested as hybrids are most likely introgressants. Hy bridization and introgression are likely the major causes of the high varia bility previously attributed to G. chiloensis by taxonomists.