RUSSELL, ADRIENNE D. Department of Biology, San Diego State University, San Diego, CA 92182. - Phylogeny and morphology of Chorizanthe and related taxa (Polygonaceae: Eriogonoideae).
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