Date of Award

Fall 2014

Degree Type


Degree Name

Doctor of Philosophy (PhD)


Botany and Plant Pathology

First Advisor

Nancy Emery

Committee Chair

Nancy Emery

Committee Member 1

Jody Banks

Committee Member 2

Eddie Watkins

Committee Member 3

Jeff Dukes


Species' distributions are driven by a variety of abiotic and biotic factors. As these factors become altered by global climate change, species are believed to respond to these projected environmental changes in four different ways. One response is the shifting of the species' geographic range to higher latitudes and elevations, which will be unlikely for those species that have limited dispersal potential. Alternatively, organisms may tolerate the change, which will be unlikely for those organisms that are not phenotypically plastic. A third potential response is to adapt to the new environment via rapid evolution, an unlikely response for those organisms that are isolate and genetically depauperate. Therefore, those species that are characterized by limited dispersal potential and populations that are differentially adapted may be especially sensitive to the anticipated environmental changes associated with global climate change. ^ Here, we used a variety of field and common garden experiments to understand how a fern species will respond to global climate change. Specifically, we tested for dispersal limitation at the northern range boundary, population differentiation, and phenotypic plasticity. Our focal species, Vittaria appalachiana, is an asexual, gametophytic fern species, that occupies patchily distributed, non-calcareous rock shelters in the Appalachian Mountains of eastern North America. In each experiment, we used six different populations that span the species' geographic range. To test for dispersal limitation, transplants were placed in a site beyond the northern range boundary that does not contain any known V. appalachiana populations. Transplants from each of these populations were also reciprocally transplanted amongst each population to test for local adaptation. Finally, explants from each of the six source populations were exposed to various temperature and humidity conditions, to test for phenotypic plasticity in response to temperature and humidity. ^ Cumulative results from these three studies indicate that dispersal limitation heavily influences the contemporary northern range boundary of V. appalachiana and that populations are differentially adapted. However, this differentiation is not driven by temperature or humidity. Additionally, our results also indicate that southern populations may be locally adapted, while the most northern population is composed of robust genotypes. Finally, it appears that the species as a whole prefers cooler temperatures and lower humidity levels, suggesting that global climate change may negatively impact this species. Broader implications of this study suggest that abiotic factors other than temperature may drive species' distribution patterns, and must therefore be included in modeling efforts to understand species response to climate change. Additionally, these results indicate that conservation efforts should consider population-level differences, as they may exhibit different responses to the stressors associated with global climate change