Phacelia Dubia in South Carolina: The Interface of Morphology, Genetics, and Taxonomy

Document Type


Publication Date



Three taxonomically recognized, allopatric, and ecologically differentiated varieties comprise Phacelia dubia (L.) Trel. (Hydrophyllaceae). Although widespread in the southeastern United States, the distribution and taxonomic affinities of P. dubia have been overlooked in South Carolina. Populations of P. dubia occurring on Piedmont granite outcrops in seven South Carolina counties have been referred to as putative variety "imitator." Artificial hybridizations with P. dubia var. dubia and var. georgiana McVaugh produced partially sterile F1 hybrids. Hybrids with var. interior Fern. were mostly fertile except for occasional unidirectional sterility. The fertility distributions of backcross progenies of both var. dubia-"imitator" and var. georgiana-"imitator" F1 hybrids to "imitator" parents were bimodal, and fertility was associated with one allozyme and two DNA markers, suggesting a major segregating factor controls hybrid fertility. In contrast, "imitator" is not morphologically distinct relative to vars. dubia and georgiana. Conflicting morphological, ecological and reproductive data highlight the problem of taxonomic recognition of a morphologically cryptic entity.