Systematics of Saxifraga rufidula and related species from the Columbia River gorge to southwestern British Columbia

In the Pacific Northwest, hybridization and polypoid variation have produced confusion in the relationships among Saxifraga rufidula (Small) James Macoun and its relatives. The entities from the Columbia River Gorge are particularly difficult to separate taxonomically. Some authors have recognized several species from that area while others recognize one highly variable, widely distributed species with varietal components. The present study approached the systematic treatment of S. rufidula and related subspecific taxa of S. occidentalis Wats. with data from numerical studies, studies of meiosis, observations of artificial and natural hybrid individuals and populations, breeding system experiments, observations of pollinators, and ecological observations. Polyploid intermediates and plants with introgressant characteristics are shown to occur, many of which appear to be the result of hybridization with the S. integrifolia species complex. Sufficient correlations of morphological, ecological and geographic discontinuities exist to substantiate the treatment of S. rufidula. S. occidentalls var. latipetiolata, S. occidentalis var. dentata, and S. occidentalis var. occidentalis as a species. According to the rules of nomenclature S. rufidula becomes S. aeguidentata. S. occidentalis var. latipetiolata becomes S. latipetiolata, S. occidentalis var. dentata becomes S. gormanii. and S. occidentalis var. occidentalis becomes S. occidentalis.Science, Faculty ofBotany, Department ofGraduat