Molecular evolution and population genetics of duplicated floral regulatory genes

Duplicated genes are the building blocks for the origin and diversification of gene families and may play a pivotal role in organismal diversity. Many regulatory genes involved in key developmental pathways are derived from gene duplications and divergence processes. This dissertation research examined the molecular evolution and population genetics of duplicated floral regulatory genes.; The molecular evolution of the ancestral APETALA3/ PISTILLATA gene duplication and the more recent APETALA1 /CAULIFLOWER duplication was analyzed among four taxonomic levels. The CAULIFLOWER (CAL) locus is evolving at a significantly faster rate than its paralog APETALA1 (AP1) and significant differences in substitution distributions exist along the lengths of these genes, reflecting the possible adaptive differentiation between CAL from AP1. The APETALA3/PISTILLATA paralog pair does not have detectable substitution pattern differences. These results suggest that altered rates and patterns of sequence evolution in duplicated genes may lead to divergence in developmental functions and that the gross morphological features present in these species may be due to low-level changes in nucleotide diversity.; The molecular population genetics of duplicated APETALA1 and APETALA3/TM6 orthologs was investigated in three species from two different Hawaiian silversword alliance sublineages (Argyroxiphium sandwicense, Dubautia ciliolata, and Dubautia arborea). Comparisons of these duplicated orthologs ( ASAPETALA1-A, ASAPETALA1-B and ASAPETALA3/ TM6-A, ASAPETALA3/TM6-B) in A. sandwicense and D. ciliolata indicate that two regulatory gene homoeologs (ASAP1-A and ASAP1-B) appear to be evolving in a similar fashion while the other two homoeologs ( ASAP3/TM6-A and ASAP3/ TM6-B) have patterns consistent with divergent evolutionary trajectories. This divergent evolution between two homoeologous regulatory selective forces may differ between these two gene copies.; A final study compared morphological divergence between two recently derived sibling species (Dubautia ciliolata and D. arborea) to the genetic divergence across six genes. These two species differ significantly in morphologies; yet have a genetic distance similar to levels expected between intraspecific populations. Haplotype divergence, likelihood ratio tests of exponential growth rate, and Bayesian coalescent simulations of migration and divergence across these genes among three species provide insights into demographic patterns associated with the evolution of these adaptively radiating species.