Allozymic Differentiation among Heuchera americana, H. parviflora, H. pubescens, and H. villosa (Saxifragaceae)

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Abstract
Heuchera americana, H. parviflora, H. pubescens, and H. villosa are diploid, herbaceous perennials native to eastern North America. Starch gel electrophoresis was used to estimate the amount of genetic divergence among these four species. Mean genetic identities for populations of H. americana, H. parviflora, H. pubescens, and H. villosa are 0.98, 0.98, 1.00, and 0.99, respectively. The mean genetic identity for pairwise comparisons of populations of all four species is 0.92, indicating a high degree of allozymic similarity among these species. Isozyme data suggest two pairs of closely related species: H. americana and H. pubescens; and H. parviflora and H. villosa. The mean genetic identity for populations of H. americana and H. pubescens is 0.99, while the value for populations of H. parviflora and H. villosa is 0.98. In contrast, mean genetic identity values for all other species comparisons are less than 0.90. Within each of these two species pairs the members are highly interfertile and isolated ecologically in nature. Speciation in this group apparently occurs with little divergence at genes coding for isozymes.