Patterns of Isozyme Variation in Western North American Antennaria (Asteraceae: Inuleae). I. Sexual Species of sect. Dioicae

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Abstract
Antennaria is a genus of dioecious, perrenial herbs, widely distributed throughout temperate and arctic North America and Eurasia. Four sexually reproducing, primarily diploid species (2n = 28) in section Dioicae from western North America were investigated for genetic differentiation at 19 putative isozymes. Antennaria corymbosa, A. marginata, A. microphylla, and A. rosulata are morphologically distinct, but display only moderate divergence at gene loci specifying soluble enzymes. Some correlations exist between genetic distances and geographic patterns within the species examined. Neighboring populations tend to be more similar electrophoretically than geographically distant or marginal ones. The inferred mode of speciation, based on morphology and biochemical genetics, is one in which rapid evolution (adaptive radiation) has occurred, leading to morphological divergence, but only conservative amounts of divergence at the 19 isozymes surveyed.