Taxonomy of the Ipomopsis aggregata Group (Polemoniaceae)

The highly variable Ipomopsis aggregata complex (Polemoniaceae) is revised on the basis of extensive field and herbarium study. A three-species system consisting of I. aggregata, I. arizonica, and I. tenuituba is adopted. Seven geographical subspecies are recognized in I. aggregata, namely, subspecies formosissima, aggregata, bridgesii, collina, attenuata. weberi subsp. nov., and candida. In their geographical and breeding relationships the first five subspecies are geographical races, and the last two are semispecies. Geographical variations are described but not recognized taxonomically in I. arizonica and I. tenuituba. Local racial variation is common in the group, and examples are listed for most taxa. Hybridization occurs locally between I. aggregata and I. tenuituba.