Document Type



Doctor of Philosophy


Biology, Plant Systematics

Date of Defense


Graduate Advisor

Elizabeth A. Kellogg, Ph.D.


Al-Shehbaz, Ihsan


Stevens, Peter F.

Pires, Chris J.


The mustard family (Brassicaceae) is economically important but the evolution of its morphology is not well understood. I investigate the evolution of morphological and genomic characters and calculate ancestral trait values in the Brassicaceae within a phylogenetic context using the tribe Physarieae as a model system. Physarieae are a unique and diverse group of American mustards characterized by multi-aperturate pollen. Phylogenetic analyses of DNA sequences (chloroplast ndhF and nuclear ITS and LUMINIDEPENDENS) were used to test the monophyly and explore evolutionary relationships of Physarieae. The phylogenetic inferences were used to identify morphological traits to delimit the tribe, to interpret the evolution of selected morphological and genomic characters, and to test alternative hypotheses related to the covariation of traits. Results show that Physarieae are monophyletic and most closely related to three tribes (Halimolobeae, Boechereae, Camelineae) based on analyses of parsimony, likelihood, and Bayesian analyses. Two well-supported monophyletic clades in the tribe are recovered: the DDNLS clade, including Dithyrea, Dimorphocarpa, Nerisyrenia, Lyrocarpa, and Synthlipsis, and the PP clade, comprising Paysonia and Physaria. Character optimization of discrete and continuous morphological data suggest that enlarged fruits and replums, wide seeds, and long fruiting styles are potential synapomorphies of Physariae, whereas traits related to fruits, seed, trichomes, and pollen are useful to distinguish groups and genera within the tribe.

OCLC Number


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