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Genetic variation in Hydrastis canadensis populations in western North Carolina

WCU Author/Contributor (non-WCU co-authors, if there are any, appear on document)
Jennifer Marian Torgerson (Creator)
Institution
Western Carolina University (WCU )
Web Site: http://www.wcu.edu/404.asp
Advisor
Laura DeWald

Abstract: Goldenseal (Hydrastis canadensis L.) is a herbaceous perennial that is broadly distributed in patches in eastern deciduous forests. This plant is a valuable medicinal herb, and overharvest has been a cause of population decline along with loss of habitat. Because goldenseal reproduction mostly occurs clonally through rhizome growth and patches are usually small, dense, and highly isolated, genetic diversity within a patch is thought to be relatively low, but little is actually known about goldenseal genetics. Genetic variation is important for species in changing environments because a diversity of alleles provides a possibility for genetic adaptation. This project measured the genetic variation in six natural populations of goldenseal in western North Carolina using an allozyme analysis on leaf material collected from the field to measure molecular genetic diversity and a common garden experiment using rhizomes transplanted from the field to measure phenotypic genetic diversity. Half the rhizomes for the common garden experiment were grown in a greenhouse and the other half under a lath house. Rhizomes were cut in half, producing genetic clones, and one half was given a high fertilizer treatment and the other half low fertilizer. Phenological traits, measured at the end of the growing season, showed more phenotypic variation between than within populations for emergence and dieback dates, percent reproduction, and biomass. Fertilizer was a significant factor in differences in biomass and dieback timing, but growth area was not a significant source of variance for any trait. Additionally, no significant interaction between genetics (population) and the environment (fertilizer level) was found (i.e. no GxE), which indicated a lack of local adaptation and suggested goldenseal may be a genetic generalist. A separate field study revealed significant differences among populations in rhizome content of medicinal alkaloids. Results from the allozyme analysis on the same populations as used in the common garden indicated more genetic variation within than between populations, so these populations are not diverging genetically. However, even within populations diversity was very low. The molecular diversity present could be due to sexual reproduction. To encourage sexual reproduction and the maintenance of genetic diversity, it may be beneficial to add substrate disturbance and canopy gaps to populations with the greatest conservation needs. Additionally, because fertilizer increased biomass, which was associated with higher reproduction, adding fertilizer at time of disturbance could increase population growth through increased clonal spread and sexual reproduction.

Additional Information

Publication
Thesis
Language: English
Date: 2012
Keywords
allozymes, common garden, genetic diversity, medicinal herb, rare plant
Subjects
Goldenseal -- North Carolina, Western -- Genetics