Picture of Valerie Soza
Valerie L. Soza
Department of Biology, University of Washington
Box 351800, Seattle, WA 98195-5325
A spacer for table designCurriculum Vitae

Galium grande (sect. Baccogalium)

Galium hypotrichium var. tomentellum (sect. Lophogalium)


My research attempts to understand the evolutionary history of species and the potential role that polyploidy plays in speciation of angiosperms. In particular, I am interested in the role of polyploidy in the evolution of sexual systems and other key morphological features related to diversification.


My postdoctoral research in the Di Stilio lab examined 1) the evolution and correlation of pollination mode, sexual system, polyploidy and genome size in the genus Thalictrum (Ranunculaceae; Soza et al. 2012, 2013), 2) the evolution and development of separate sexes in the genus Lepidium (Brassicaceae; Soza et al. 2014), and 3) functional divergence of gene duplication in the floral organ identity E-class genes in Thalictrum.


My doctoral research in the Olmstead lab examined the evolutionary history of tribe Rubieae, in particular, the evolution of sexual systems, leaf whorls, and systematics of Galium and related genera in the Rubiaceae (coffee family; Soza and Olmstead 2010).

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 species, rarely occurs in flowering plants but has often been considered an intermediate sexual form.

My work 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 provided an opportunity to test Dempster's original hypothesis (1973) that species exhibiting polygamy are evolving towards dioecy from a state of hermaphroditism (Soza and Olmstead, 2010).

For results on the evolutionary relationships within Rubieae, evolution of sexual systems, and implications for species management of rare taxa within Galium, please see publications listed on my CV or my dissertation.

For images of Galium species and field work conducted during my dissertation, please see my image galleries.


Galium oreganum (sect. Platygalium)

Galium hirtum (sect. Relbunium)
(Photo by J.T. Columbus)