The subfamily Eriogonoideae is a diverse group of shrubs, herbaceous perennials, and annuals that is characterized by the absence of sheathing leaf stipules (ocrea), and the presence of a whorl of inflorescence bracts subtending each inflorescence node and a whorl of involucral bracts subtending each flower or cluster of flowers. The majority of taxa in the subfamily are aligned with one of two large genera, Eriogonum (wild buckwheat, ~240 spp.) and Chorizanthe (spineflower, 40 N. American spp.). The remaining 15 genera in the subfamily are small, largely monotypic taxa. Relationships within Chorizanthe and within the Eriogonoideae were examined through parsimony analysis of 93 taxa using 80 non-molecular characters. The analysis included 42 species of Chorizanthe, 40 additional members of the Eriogonoideae, and eleven outgroup taxa representing Polygonaceae and Plumbaginaceae. The objectives of this study were to assess (1) monophyly of Chorizanthe , (2) interspecific relationships within Chorizanthe, and (3) intergeneric relationships within the subfamily Eriogonoideae. Data presented are from studies of vegetative morphology, inflorescence structure, floral and fruit morphology, and palynology. Morphological character evolution is discussed as it pertains to classical and revised (phylogenetic) definitions within the eriogonoid taxa. The study points to extensive variation in floral and inflorescence morphology in the subfamily Eriogonoideae and recognizes the high level of homoplasy in this group of specialized annuals and related perennials. In addition, newly discovered variation in pollen ultrastructure of Chorizanthe species will be presented.

Key words: Chorizanthe, Eriogonoideae, Eriogonum, involucre, phylogeny, Polygonaceae