Date of Award
Master of Science
Entomology and Plant Pathology
Margaret E. Staton
Phillip A. Wadl, Edward E. Schilling, Robert N. Trigiano
Pityopsis (Asteraceae) includes seven species; one species, P. ruthii, is federally endangered. The genus exhibits a range of ploidy levels, widespread hybridization among species with overlapping ranges, and interesting adaptive traits such as fire-stimulated flowering. However, taxonomy of Pityopsis has remained unresolved. Resolving interspecific relationships can lead to a deeper understanding of the inheritance and hybridization patterns, as well as the evolution of adaptable traits. Our first objective was to examine population structure and gene flow within Pityopsis ruthii. Polymorphic microsatellite markers (7 chloroplast and 12 nuclear) were developed and used to examine genetic diversity of 814 P. ruthii individuals from 33 discrete locations along the Hiwassee and Ocoee Rivers. A total of 198 alleles were detected with the nuclear loci and 79 alleles with the chloroplast loci. Bayesian cluster analyses of both rivers identified six clusters when the chloroplast microsatellites were used, whereas only two clusters were identified from the nuclear microsatellites. The population structure of P. ruthii will allow delineation of conservation units that account for subpopulations along each river. Our second objective was to examine the relationships of the seven species within Pityopsis using phylogenetic analyses. The chloroplast genome was sequenced for six species and two varieties. A reference chloroplast genome was assembled de novo from P. falcata, the species with the highest depth of read coverage. Reads from seven other individuals were then aligned to the P. falcata chloroplast genome and an individual genome was assembled for each. To utilize all informative sites for the full length of the chloroplast, a multiple sequence alignment of the eight chloroplast genomes was constructed, and from this, a phylogeny using both the maximum likelihood and maximum parsimony methods. Our findings using the entire chloroplast genome deviate from the results of previous phylogenetic studies of Pityopsis and do not support previously defined clades or sections within the genus. Our two objectives add meaningful information about the diversity of P. ruthii and the evolutionary history of Pityopsis, now available for use by conservationists, molecular ecologists, and evolutionary biologists.
Hatmaker, Elizabeth Anne, "Population genetics and genomics within the genus Pityopsis. " Master's Thesis, University of Tennessee, 2016.