I am a conservation biologist, landscape ecologist and population geneticist. My central research interest is the genetic conservation of imperiled forest tree species, including those decimated by exotic pests and at risk from climate change.
To that end, I have employed a variety of molecular genetic markers to quantify the genetic diversity of such species as Fraser fir (Abies fraseri), eastern hemlock (Tsuga canadensis), Carolina hemlock (Tsuga caroliniana), and ocote pine (Pinus oocarpa).
Additionally, I am interested in better understanding evolutionary processes from a landscape ecology perspective and in the context of conservation biology. Among other things, I am working with fellow landscape ecologists to use geographic information system (GIS) tools to assess the potential impacts of climate change on the genetic integrity of North American forest tree species.
I am enthusiastic about engaging bright and motivated students in the exploration of ecology, conservation science, and natural resource management. At NC State University, I developed and taught a Plant Conservation special topics course for upper-level undergraduates and graduate students, and I taught a segment on water resource and wetland management for an undergraduate Environmental Impact Assessment course. I also twice taught the field laboratory section of Dendrology, the woody plant identification and biology course required of all undergraduate Forestry majors.
Finally, I am lead editor of the US Forest Service's annual Forest Health Monitoring national technical report on the health of U.S. forests. In addition to allowing me to pursue my interests in landscape ecology and conservation biology, this puts my previous communications experience to use. (My undergraduate degree is in journalism, and I spent four years as a newspaper reporter and four years as a university writer and editor.)
Following are brief descriptions of my three main research interests:
1) Assessing forest tree risk of extinction and genetic degradation as a result of climate change
Collaborators:
Bill Hargrove, Eastern Forest Health Environmental Threat Assessment
Center (http://forestthreats.org/), USDA Forest Service, Southern Research Station
Frank Koch and Fred Cubbage, Department of Forestry and Environmental Resources, North Carolina State University
Climate change is expected to pose a severe threat to the viability of forest tree species, which will be forced either to adapt to new conditions or to shift their ranges to more favorable environments.
Climate change is a priority area identified by the Forest Health Monitoring program of the USDA Forest Service, which is sponsoring a baseline assessment of the risk that climate change poses of genetic degradation, local extirpation or species-wide extinction to North American tree species. This project has three main objectives: 1) Forecast the location and quality of habitat for at least 100 North American tree species under two climate change scenarios, for the years 2050 and 2100. 2) Measure the minimum required migration distance from each species’ current location to the nearest favorable future habitat. Information on the locations of future refuges will be integrated with existing forest fragmentation data to quantify the quality of those refuges and to determine the amount of biotic “resistance” species are likely to encounter as their ranges shift toward those refuges. 3) Assess, with the assistance of other forest geneticists and ecologists, the susceptibility of forest tree populations to genetic degradation and extirpation based on these results and on each species’ biological characteristics.
Central to this study is the Multivariate Spatio-Temporal Clustering (MSTC) technique (Hargrove and Hoffman 2005), which combines aspects of traditional geographical information systems and statistical clustering tools to statistically model environmental niche envelopes, which can be used to forecast a species’ geographic range under climate change. Incorporating more than a dozen spatial environmental variables, it will predict the future location and quality of habitat for tree species and, along with consideration of species’ biological attributes, will allow for an assessment of whether migrating species might be able to track the appropriate environmental conditions over time and avoid the loss of extensive genetic variation.
The primary products of this work will be a set of large-scale, 4-km2 resolution maps for each of the tree species included in the study. These will be packaged and available to the public through a new online atlas of climate change genetic risk for North American forest trees. These should be valuable for scientists and policymakers attempting to determine which forest tree species and populations, in the face of climate change, should be targeted 1) for monitoring efforts, 2) for in situ and ex situ conservation actions, and 3) for molecular marker studies that quantify the genetic architecture and diversity of at-risk species. The results also should be useful for land-use planners and conservation organizations interested in identifying geographic locations that could be preserved as important future habitat for at-risk tree species.
2) Investigating evolutionary relationships among species as a tool for assessing forest health
Collaborator:
Frank Koch, Department of Forestry and
Environmental Resources, North Carolina State University
Genetic diversity is a central component of forest sustainability, a fact recognized in the Montreal Process criteria and indicators of forest sustainability. A new approach now makes it possible to measure genetic variation for entire communities of forest trees, rather than only a handful of individual indicator species inhabiting forest ecosystems. Phylogenetic community analysis does this by calculating the cumulative evolutionary age of all the species in a community based on their position on a phylogenetic “tree of life,” which depicts the evolutionary relationships among species based on gene sequencing studies and surveys of the fossil record.
An analysis quantifying forest community evolutionary diversity across the conterminous United States, using data from more than 100,000 Forest Inventory and Analysis plots, is the first of its kind at a continental scale. This is of particular interest in the context of conservation, because evolutionary diversity is arguably a more biologically meaningful measurement of biodiversity than traditional statistics such as species richness and abundance. This kind of analysis also has forest health implications because it reveals patterns of “phylogenetic clustering,” where species within forest communities are more closely arranged on the evolutionary “tree of life” than expected by chance, and therefore may be more susceptible to certain forest threats. Future work will, among other things, use the evolutionary relationships among host species to generate maps of pest and pathogen risk to the evolutionary diversity of forest communities. Such maps represent a useful tool for scientists and land-use planners working to maximize forest biodiversity and forest health.
3) Evaluating genetic variation and conserving genetic variattion of forest tree species threatened by insects and diseases
Collaborators:
John Frampton, Christmas Tree Genetics Program , Department of Forestry and Environmental Resources, North Carolina State University
Bill Dvorak, Camcore,
Department of Forestry and Environmental Resources, North Carolina State University
Ross Whetten, Department of Forestry and
Environmental Resources, North Carolina State University
Much of my recent research work has centered on the population genetics, evolutionary history, and genetic conservation of conifers, particularly those that are rare and/or infested by pests or pathogens. Specifically, I am interested in the effects of small population size, in the spatial arrangement of genetic variation on the landscape, and in the effect of post-Pleistocene migration history on the phylogenetic relationships among species.
Genetic response to fragmentation and small population size: Population genetic theory predicts that small population size should increase the chance of detrimental genetic processes, including inbreeding and genetic drift. To test these predictions, my dissertation work included a population genetics analysis of Fraser fir (Abies fraseri), which exists as a set of populations in varying size and distance from each other. The results of the microsatellite molecular marker study suggested that smaller populations did not suffer more extensively from detrimental genetic effects, and that the genetic architecture of the species is more likely the result of its post-glacial migration history. A series of mathematical matrix models, meanwhile, led me to conclude that Fraser fir populations are large enough, and the species’ life cycle long enough, to avoid genetic drift after a single infestation by the exotic balsam woolly adelgid (Adelges piceae), but not after repeated infestations over several centuries. These results were incorporated into an ex situ gene conservation strategy I developed for Fraser fir.
Phylogeography of conifers: I am highly interested in the evolutionary history of plant species since the end of the most recent Pleistocene glaciation roughly 12,000 years ago. The ranges of plant species shifted dramatically in the following millennia, influencing the patterns of genetic variation present in those species today. Using microsatellite markers, my dissertation research concluded that balsam fir (Abies balsamea) probably existed in three refugia during the Pleistocene, and that closely related Fraser fir is likely an adaptive extreme of balsam fir that lost genetic contact with it during post-Pleistocene isolation. As part of my postdoctoral work at Camcore, I helped to conduct a molecular marker study of eastern hemlock (Tsuga canadensis) in the Southeastern United States, to better understand the genetic architecture of this species, which is being decimated by the exotic hemlock woolly adelgid (Adelges tsugae). The study determined that greater genetic diversity exists east of the southern Appalachian Mountains, suggesting that the Pleistocene refuge for the species was in this area. An extension of this project now includes eastern hemlock populations throughout the eastern United States.
Evolution of pest and disease resistance: Population genetics tools may offer insights into the evolution of adaptive traits such as pathogen or pest resistance. I recently helped to conduct the most complete population diversity study attempted to date on Pinus oocarpa and its close relatives in Mexico and Central America. One goal of the study was to trace the evolution of pitch canker resistance in these taxa, as P. oocarpa is entirely resistant while some provenances of P. tecunumanii and P. patula are partially resistant.
Molecular systematics of true firs: I am working with colleagues in the Department of Forestry and Environmental Resources to use chloroplast gene sequencing to elucidate evolutionary relationships among the true firs (Abies). The taxonomy of the true firs is controversial, in part because of the existence of intermediate forms between several pairs of closely related sibling species, and because of the extent of genetic introgression and ease of hybridization among Abies species with overlapping ranges. The results may offer insights into differences among Abies species in susceptibility to Phytophthora root rot (Phytophthora ramorum).
