Galium grande (sect. Baccogalium)

Galium hypotrichium var. tomentellum (sect. Lophogalium)

My current research focuses on the evolution of plant sexual systems and systematics of Galium and related genera in the Rubiaceae (coffee family).

Various evolutionary pathways have been proposed to explain the evolution of dioecy, the separation of reproductive organs on different individuals, from hermaphroditism. Polygamy, the occurrence of both hermaphroditic and unisexual flowers within a taxon, has often been considered an intermediate sexual form. Polygamy does not occur commonly among angiosperms and examining a group that contains both hermaphroditic and dioecious species, as well as polygamous species, will aid our understanding of the evolution of this particular sexual system.

The genus Galium is distributed worldwide and has traditionally been divided into 15 sections. Molecular analyses of the cpDNA trnL-ndhJ, rpoB-trnC, and trnC-psbM regions confirm previous analyses by Manen et al. (1994) and Natali et al. (1995), demonstrating that Galium, as traditionally circumscribed, is not monophyletic.

This work has identified a clade comprised of members of 5 traditionally circumscribed sections - Baccogalium, Bataprine, Lophogalium, Platygalium, and Relbunium. The occurrence of polygamy, dioecy, and hermaphroditism within this group provides an opportunity to examine sexual system evolution. A molecular phylogeny is being constructed for this clade to test Dempster's original hypothesis (1973) that species exhibiting polygamy are evolving towards dioecy from a state of hermaphroditism.

BIOL117/317 Plant Identification & Classification

University of Washington, Department of Biology

Olmstead Lab

University of Washington Herbarium (WTU)

Rancho Santa Ana Botanic Garden (RSA)

Third International Rubiaceae Conference

Fourth International Rubiaceae Conference