This thesis investigates the molecular evolution of the cytosolic glyceraldehyde 3-phosphate dehydrogenase (GapC) gene family in two varieties of Amsinckia spectabilis (Boraginaceae) that differ in mating system. Examination of sequence variation suggests that the gene family consists of three or four members. Compared with GapC in Arabidopsis thaliana, the GapC locus in A. spectabilis has at least two fewer introns and one intron that is double in length. Strong purifying selection was detected at each putative locus since the divergence of the Amsinckia spectabilis lineage from species in the allied family Solanaceae. Mean nucleotide diversity across all observed loci is 0.0036 for the inbreeding variety spectabilis, and 0.0049 for the outbreeding variety microcarpa . Outbreeding populations were systematically more diverse than inbreeding populations at GapC-IV. These results are discussed in the context of theory for the fate of duplicate genes, and the background selection hypothesis.

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