Date of Award
8-2025
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Biological Sciences
Committee Chair/Advisor
Saara J. DeWalt, Advisor
Committee Member
Christopher L. Parkinson, Committee Chair
Committee Member
Elizabeth A. Cooper
Committee Member
Amy L. Lawton-Rauh
Committee Member
Skip J. Van Bloem
Committee Member
Joan L Walker
Abstract
Population survival or extirpation may be dependent on adaptation to local environmental conditions. I hypothesized that populations of species with large ranges would be locally adapted because of the variety of environments that different populations experience, that spatial patterns of local adaptation would correspond to patterns of endemism because processes driving local adaptation may also lead to speciation, and that the extent of local adaptation would be stronger in species with little gene flow among populations than in those with extensive gene flow because of the relative strength of selection necessary to overcome gene flow. I tested these hypotheses using three wide-ranging plant species that are important components of the ground layer in the endangered Pinus palustris ecosystem where knowledge of local adaptation could have important implications for ecosystem restoration efforts: Lespedeza capitata, Solidago odora, and Tephrosia virginiana. I also determined which strategy of choosing seed for use in ecosystem restoration best accounted for local adaptation: geographic or environmental distance between source and restoration site or ecoregion common to both sites. I found evidence of local adaptation in two of the three species based on genotype-environment associations. Isolation-by-environment (IBE) explained substantial adaptive divergence among populations as did isolation-by-distance (IBD). IBE and IBD were correlated, but the lack of population structure suggested that adaptive divergence was due to local adaptation. Patterns of adaptive genomic divergence among populations corresponded to patterns of plant endemism at the scale of the entire range of Pinus palustris, but they didn’t match patterns of plant endemism within the Mid-Atlantic and South Atlantic Coastal Plains. Among species, the relative extent of local adaptation matched predictions based on levels of gene flow within species. However, there was no consistent performance advantage of local plants over non-local plants when grown in a common garden. For restoration of the Pinus palustris ground layer, using seed from sources closest to restoration sites or from within the same TNC ecoregion as restoration sites would be reasonable strategies. However, I recommend using multiple sources based on environmental similarity to account for local adaptation/
Recommended Citation
Joines, Jason Paul, "Local Adaptation in the Pinus palustris Ground Layer" (2025). All Dissertations. 3970.
https://open.clemson.edu/all_dissertations/3970