Sectional integrity in Linanthus (Polemoniaceae): A molecular phylogeny ofsection Dianthoides

The 44 species of Linanthus are arranged into six sections based on morphol ogical features. Five of the sections are readily circumscribed and have no t presented infrageneric problems to botanists. Section Dianthoides, howeve r, is not morphologically cohesive It consists of eight annual species sens u Grant with diverse ranges and habitats in southern California and norther n Baja California. Vegetative and floral features suggest that the section, as traditionally defined, may not be monophyletic However, these morpholog ical characters do not offer a clear view of relationships among the specie s of sect. Dianthoides or of the section within Linanthus. To test the mono phyly of sect. Dianthoides and to decipher relationships among the species, we conducted a phylogenetic analysis using sequence data from the ITS regi on of nuclear ribosomal DNA. We sampled all ten species from both Grant and Patterson's treatments of sect. Dianthoides and at least one species from each of the other five sections. These data support a paraphyletic Linanthu s, which is consistent with the findings of other molecular studies. Trees obtained show two primary lineages of Linanthus: one comprising sect. Diant hoides, two species of sect. Linanthus (sensu Grant), members of Leptodacty lon, and two species of Gilia, and a second lineage composed of the remaini ng four sections of Linanthus and Phlox.