Analysis of hybridization betweenGrindelia brachystephana andG. chiloensis (Asteraceae: Astereae) in Patagonia, Argentina

Intermediates between two South American species ofGrindelia were found in Chubut Province, Argentina. Twenty eight individual plants with phenotypes ofG. brachystephana, G. chiloensis, or intermediates were collected and studied together with three reference specimens of each of the putative parental species. Discriminant analysis procedure and the computer program HYWIN were applied and results of the two methods are compared. Results demonstrate that most of the specimens collected are of hybrid origin, and that most of the specimens suggested as hybrids are most likely introgressants. Hybridization and introgression are likely the major causes of the high variability previously attributed toG. chiloensis by taxonomists.