Gilia sinistra remains one of the more enigmatic species of Polemoniaceae. Formally recognized in the early 1900's, this small-flowered plant was afterward considered synonymous with G. capillaris. A larger-flowered form was also later described as a subspecies of G. leptalea. These two forms were united under the name Gilia sinistra in 1993. Concomitantly, all three of the above species were circumscribed in a new section of Gilia, section Kelloggia. Cohesive in gross morphology but variable in geographic distribution and breeding systems, the species of section Kelloggia provide an interesting model for exploring patterns of diversification among a putatively monophyletic group. Isozyme analyses of 24 populations, however, reveal unexpected divergence within Gilia sinistra. Analyses of chloroplast and nuclear DNA sequences also reveal this remarkable divergence. Instead of a monophyletic group, section Kelloggia comprises three distinct lineages, all with affinities to Navarretia. Gilia leptalea and G. capillaris form one lineage, and G. sinistra occurs in two well-separated lineages. The geographic distribution of the morphologically cryptic races of G. sinistra were determined from sampling DNA sequences from over 30 populations throughout its range. The proper application of the specific epithet to one of these races was determined by scrutiny of micromorphological characters among these populations and the nomenclatural type. Combined, these data suggest possible reticulate evolution in the origin of at least one of the sinistra lineages. These data also favor the recent realignment of the kellogioid gilias in Navarretia, rather than in Allophyllum as also recently proposed. Although these "gilias" are readily distinguished in gross morphology from both genera, corroboration of morphological and molecular data argue for expanding the concept of Navarretia to include these species--but not as a single, exclusive section within this genus.

Key words: cryptic species, Gilia, Navarretia, phylogeny, Polemoniaceae, taxonomy