An Examination of Introgression in the Trillium erectum Species Complex Using Microsatellite Analysis.

There are seven named taxa of the Trillium erectum L. species complex that are native to North America, many of which are experiencing secondary contact and hybridizing due to a lack of reproductive isolating mechanism. This project will focus on T. erectum var. album, a white flowered taxa, T. erectum var. erectum, a red flowered taxa, and T. rugelii, a white flowered taxa, each of which occurs in the southern Appalachian Mountains and are found in populations that overlap in geographic range and flowering phenology. Using three microsatellite loci developed for a related trillium species, this study examines hybridization and genetic structure of several populations of the T. erectum species complex, located in three counties in the western region of North Carolina, to determine if different taxa growing in mixed populations are interbreeding, and if so, quantify the amount of admixture and examine what factors, taxon identity, geographic range or flower color, are most influencing hybridization. Allele frequency analyses of microsatellite loci were used to compare the populations. We performed Principle Components Analysis comparing using pairwise comparisons of both fixation index and Nei's Genetic distance calculations for each geographic population. Structure analysis was used to identify populations and quantify admixture based on allele frequency and assumptions of gene flow using Bayesian statistical methods. Results from population genetics and Structure analyses suggest that allele sharing occurs primarily based on taxon identity and geographic proximity, but flower color may also play a role in influencing gene flow. [ABSTRACT FROM AUTHOR]