Diversification of class III of the HD-Zip gene family: implications for laminar evolution in angiosperms

This thesis addresses natural history of the HD-Zip gene family, especially class III (HDZ-III). I explore patterns of sequence variation in HDZ-III across the land plants and provide estimates of the phylogenetic history of the gene family using a variety of inference methods. I also calibrate a molecular clock of the gene family and us it to provide estimates of minimum divergence times for key clades and gene duplication events in the family. I investigate patterns of gene expression for members of HDZ-III and selected members of the YABBY family. I provide evidence of clade-specific divergences in expression patterns, suggesting that promoter function changed following some ancient gene duplication events. Finally, I attempt to draw upon the phylogenetic, temporal, and gene expression data to reconstruct a tentative model of the relationships between events in the natural history of HDZ-III and the diversification of landplants.