The evolution of selfing, inbreeding depression, and polyploidy in the Claytonia perfoliata complex (Portulacaceae)

Polyploidy, the doubling of chromosomes within a species (autopolyploidy) or chromosome doubling in conjunction with hybridization (allopolyploidy), is accepted as having a major role in plant evolution. The ubiquity of polyploidy in plants indicates that polyploidization is a common form of speciation with significant ecological and genetic consequences. The objective of this research is to investigate the evolution of polyploidy; both theoretical and empirical approaches are considered.;First, theoretical models are developed to examine the role of selfing, inbreeding depression, and population size on autopolyploid establishment in mixed cytotype populations. This research is presented in Chapter One. The Second Chapter represents a response to a technical comment of Chapter One. Results from both of these chapters show that autopolyploid establishment is facilitated by increased selfing and/or lower inbreeding depression in polyploids relative to diploids. Second, molecular and quantitative population-level approaches are used to empirically examine the relationship between polyploidy, selfing, and inbreeding depression in populations of the Claytonia perfoliata polyploid complex. This is presented in Chapter Three. Results show that inbreeding depression is greatest in outcrossing populations and that ploidy has no significant effects on the level of inbreeding depression. Third, DNA-based data is used to infer phylogenetic relationships and polyploid origins among diploid and polyploidy entities in the Claytonia perfoliata polyploid complex. This is presented in Chapter Four. Results show that both autopolyploidy and allopolyploidy are common within the Claytonia perfoliata complex and that many cytotypes have multiple independent polyploid origins.