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Research Following are my research interests: · population genetics of forest tree species; · conservation biology, especially the genetic conservation of rare tree species; · landscape ecology; · population genetics-related mathematical modeling. Below is further information about current and recent research projects. Evolutionary History and Genetic Conservation of Fraser Fir (Abies fraseri) Phytophthora Root Rot Mortality in Fraser Fir: Genetic Variation in an Infested Progeny Test Landscape Characteristics and North Carolina Stream life: A Multiple-Scale Ecological Risk Assessment of Nonpoint Source Pollution Evolutionary History and Genetic Conservation of Fraser Fir (Abies fraseri) For link to a PDF version of my dissertation at the NCSU Libraries, click here. Academic advisor: Dr. John Frampton, associate professor of forestry and director of the North Carolina State University Christmas Tree Genetics Program Graduate committee members: Dr. George R. Hess, associate professor of forestry, North Carolina State University Dr. Michael D. Purugganan, associate professor of genetics, North Carolina State University Dr. Jenny Xiang, assistant professor of botany, North Carolina State University Doctoral dissertation abstract: Fraser fir (Abies fraseri [Pursh] Poir.) is a glacial relict species endemic to high peaks in the Southern Appalachians.  A conifer with considerable ecological and economic importance, it has been devastated by the infestation of the balsam woolly adelgid (Adelges piceae Ratz.), an exotic insect from Europe. I developed a series of stage-structured population matrix models for Fraser fir to simulate genetic dynamics in a long-lived forest tree species with overlapping generations.  The results suggest that Fraser fir populations are large enough and its life cycle is long enough to avoid significant genetic drift, absent repeated adelgid infestations.  The model results indicate that other forces, including natural selection and inter-population pollen exchange, are more likely to have influenced the genetic structure of the species. I used microsatellite molecular markers to assess the genetic structure and genetic diversity of Fraser fir populations.  This analysis found only slight differentiation among populations, but greater inbreeding and less observed heterozygosity than in other conifers.  No genetic diversity measure was correlated with population size, suggesting that smaller populations did not suffer more extensively from detrimental genetic effects following post-Pleistocene fragmentation.  While some gene flow may occur between populations in close proximity, the genetic architecture of the species is more likely a function of its post-glacial migratory history.  Unexpectedly, some of the smallest Fraser fir populations were the most genetically diverse by some measures, and the largest and least isolated populations were among the least diverse. Using the same microsatellite loci, I detected a relatively small amount of differentiation among Fraser fir, balsam fir (Abies balsamea [L.] Mill.), and intermediate fir (A. balsamea var. phanerolepis Fern.), suggesting that these taxa should be treated as varieties of the same species.  Balsam fir appears to consist of three demes, suggesting the possibility of one large central fir refuge during the Pleistocene, with smaller refugia to the east and west.  Fraser fir, with highly exserted and reflexed cone bracts, may represent an adaptive extreme of balsam fir that, during post-Pleistocene isolation, lost genetic contact with relatives lacking exserted bracts.  The results also indicated the probable introgression of subalpine fir (A. lasiocarpa [Hook.] Nutt.) genes into balsam fir. I conclude that in situ conservation of Fraser fir’s genetic composition is currently adequate, but may be insufficient in the face of global climate change and repeated adelgid infestations.  A concerted ex situ strategy is needed to thoroughly conserve the genetic diversity of the species.  I developed such a strategy for Fraser fir with two objectives: (1) to preserve its natural population genetic diversity in case Fraser fir populations are extirpated or degraded, and (2) to conserve and make available Fraser fir genetic resources for the breeding of an economically important tree species.  The ex situ gene conservation strategy has four central components: (1) a seed bank representing all the Fraser fir populations, (2) existing elements of tree breeding efforts, (3) conservation plantings, and (4) an archive of Fraser fir DNA. Return to top Phytophthora Root Rot Mortality in Fraser Fir: Genetic Variation in an Infested Progeny Test Research project with Dr. John Frampton Overview: Fraser fir (Abies fraseri (Pursh.) Poir.), which is native to a small number of isolated ridgetops in North Carolina, Tennessee, and Virginia, is widely grown in the Southern Appalachians for the fresh-cut Christmas tree market. Phytophthora root rot presents a serious economic limitation to these Christmas tree growers, with the majority of root rot damage caused by Phytophthora cinnamomi Rands. In 2000, a Fraser fir progeny test in Avery County, North Carolina, was unintentionally infested by P. cinnamomi. Using data from the 94 open-pollinated families at the test site, we analyzed seedling mortality with three objectives: 1) to analyze the genetic variation within the six major Fraser fir subpopulations for potential Phytophthora root rot resistance, 2) to estimate genetic parameters for these traits; and 3) to explore using a Geographic Information System (GIS) neighborhood analysis as a tool for separating potential genetic resistance to Phytophthora from uneven exposure to the pathogen. Family within source was the only variance component significantly different from zero. When the populations were analyzed separately, family variance was also significant in some sources. The results from these analyses, and from future analyses of additional mortality at the site, were compared to results from a greenhouse inoculation test in progress during the summer of 2003. In this test, Fraser fir from 120 families and all six seed sources are being inoculated with a single P. cinnamomi isolate. Our GIS analysis generated information on the proportion of dead trees near each individual in the plot. When we used this data as a covariate term in our genetic analysis of variance, the results did not result in different variance estimates and genetic parameters than without the use of the GIS-generated neighborhood mortality data. This may indicate that the single-tree non-contiguous plot design for the field study worked to reduce differences in Phytophthora exposure among Fraser fir families. Return to top Landscape Characteristics and North Carolina Stream life: A Multiple-Scale Ecological Risk Assessment of Nonpoint Source Pollution For link to a PDF version of my master's thesis at the NCSU Libraries, click here. Academic advisor: Dr. Frederick W. Cubbage, professor and department head of forestry, North Carolina State University Graduate committee members: Dr. Gary B. Blank, associate professor of forestry, North Carolina State University Dr. George R. Hess, associate professor of forestry, North Carolina State University Master's thesis abstract: Nonpoint sources of pollution may be responsible for as much as 50 percent of current water quality degradation in the United States, and as much as 70 percent in the Southeast. In this study, I used an ecological risk assessment methodology, at the watershed scale and riparian scales (zones 300, 100, and 50 feet on either side of streams), to analyze and quantify the impact of nonpoint pollution on the ecological integrity and water quality of North Carolina streams. Specifically, I determined how land-use patterns relate to aquatic ecological integrity, including the extent to which one of the most widely promoted best management practices (BMPs) - the preservation of riparian vegetated buffers - correlates with better ecological integrity. The central goal of this project was the creation of a set of empirical models that describe the vulnerability of North Carolina aquatic ecological integrity - as measured by benthic macroinvertebrate community structure - to changes in the landscape-scale sources of nonpoint pollution. The models, the result of multiple regression analysis of Geographic Information System (GIS)-derived data, take into account watershed land form characteristics and three land cover types: forest, urban, and agriculture. The results can be used by managers and policymakers to weigh the risks of management and policy decisions for a given watershed or set of watersheds, including whether vegetated riparian buffers are ecologically effective and economically efficient in achieving water quality standards. The results of this study indicate that (1) landscape characteristics at the watershed scale predict variability in benthic macroinvertebrate community structure better than characteristics at the riparian scale; (2) land cover variables are of secondary importance to certain land form features, but are still significant predictors of macroinvertebrate community structure; (3) developed land use is the most important land cover variable at the watershed scale, while forested land cover is the most important at the riparian scale; (4) wider riparian buffer zones yield only minor differences in invertebrate community structure; and (5) more research is needed on how these interactions vary by the size of a watershed and the ecoregion in which it is located. The ecological risk assessment process that produced these results was relatively simple and inexpensive. The results are straightforward and generally easy to interpret. The vulnerability model equations that resulted from this assessment process can provide a basis for quantitatively comparing, ranking, and prioritizing risks, which can be useful in cost-benefit and cost-effectiveness analyses of alternative management options. Specifically, they offer a useful approach for characterizing the risk of potential land management options through the simulation of land use change, such as conversion of land cover or implementation of best management practices. Return to top Last updated October 19, 2007 The material located at this site is not endorsed, sponsored or provided by or on behalf of North Carolina State University.