Date of Award


Document Type

Access Controlled Thesis

First Advisor

Elizabeth McCarthy


The evolution of angiosperms has relied on pollinators to facilitate speciation. Various pollinators are attracted to distinct flower colors produced by different combinations of pigments. The flavonoid biosynthetic pathway (FBP) works in a branched pattern to produce flavonol and anthocyanin pigments, including pelargonidin (red), cyanidin (magenta), and delphinidin (purple). The objective of this study is to evaluate evolutionary pressures acting on FBP genes affecting flower color shifts in Nicotiana species. We aligned DNA sequences, inferred phylogenies, then ran both branch model and branch-site model analyses to identify the ratio of the rates of nonsynonymous to synonymous mutations (dN/dS). In branch models, some genes are under more relaxed purifying selection in species that do not produce anthocyanins, suggesting that there is less pressure to maintain these sequences. In branch-site models, some genes had some amino acid sites under positive selection, suggesting that those sites may be important in producing different pigments.