Microsatellite genetic diversity of northern red oak (Quercus rubra L.) in western North Carolina pre- and post-chestnut blight and pre- and post-harvest

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

Abstract: The impact of harvest and the loss of the American chestnut (Castanea dentata (Marsh)Borkh) was examined in northern red oak (Quercus rubra L.) (NRO) using nine microsatellite markers. Four sites located in the Nantahala National Forest in western North Carolina were considered. Each site contained a stand that had not been harvested since the removal of American chestnut circa 1920 and a stand with a more recent harvest history. Comparisons between individuals present in the stands prior to the harvest and individuals regenerated in the stand after the harvest as well as in unharvested stands between pre- and post-chestnut (Cryphonectria parasitica (Murill) Barr) blight populations indicated no significant differences in genetic diversity measures including total number of alleles (AT), mean number of alleles per locus (A), number of private alleles, observed heterozygosity (Ho), expected heterozygosity (He), latent genetic potential (LGP) and FST. Lack of genetic difference between pre- and post- harvest populations suggest NRO populations are either plastic, adapted to micro-climate changes such as those occurring as a result of a harvest, or have already undergone genetic change after the loss of the American chestnut. Significant differences were found between pre- and post- blight populations in terms of effective number of alleles (Ae), genic differentiation and specific allelic frequencies. This suggests that selective pressures in the sampled sites have been altered enough over time to precipitate some genetic change. Ecological factors that have changed in the stands since the loss of the American chestnut include reduced light availability due to change in, gap dynamics, understory species assemblages, and disturbance regime. Gap dynamics have changed post-chestnut blight in that no trees currently extant in southern Appalachian forests attain the size and therefore leave a comparable sized canopy gap as those left by the American chestnut. Understory species assemblages have changed to include a higher percentage of red maple (Acer rubrum L.), a shade tolerant species. In all stands a deficiency of heterozygotes and elevated FIS levels were detected and indicate inbreeding in the stands due to possible restricted pollen flow or habitat fragmentation. In all stands the difference in Ho versus He was greater in pre-blight or pre-harvest stands compared to post-blight or post-harvest stands. This may be attributable to change in wind movement and the resulting changes in pollen dispersal across a disturbed landscape.

Additional Information

Publication
Thesis
Language: English
Date: 2010
Keywords
microsatellites, northern red oak
Subjects
Red oak -- Adaptation -- North Carolina, Western
Red oak -- Genetics
Red oak -- Harvesting -- North Carolina, Western
Chestnut blight -- North Carolina, Western