Date of Award
Spring 2026
Document Type
Open Access Thesis
Department
Biological Sciences
First Advisor
Katherine Toll
Abstract
The evolution and maintenance of divergent populations in close proximity should be limited by the homogenizing effect of gene flow yet is often observed. In this study, we examine the evolutionary processes that contribute to this maintenance using a large-scale reciprocal transplant experiment on a mosaic of harsh serpentine soil and benign non-serpentine soil. We first examine whether local adaptation has evolved between close-proximity, edaphically contrasting populations of Mimulus guttatus. We compare the fitness of local and non-local genotypes to examine the outcome of seed dispersal between these populations and compare the fitness of the F1 and F2 hybrids to dissect whether pollen movement between the populations is likely to have a long-term homogenizing effect. Finally, we perform multivariate selection analysis on the recombinant traits of the F2 hybrids to unravel how selective pressures on characters contribute to population maintenance. We find strong evidence for local adaptation having evolved between the populations, with consistent parental fitness outcomes at serpentine site replicates but some spatial variation between non-serpentine site replicates. Maintenance of the differentiation between these populations appears to be driven by reduced survival of introduced individuals and further promoted, especially on serpentine soil, by hybrid breakdown. On non-serpentine soil, non-serpentine parents not only flowered sooner than serpentine parents, but experienced selection for this earlier flowering, which could function to limit gene flow.
Rights
© 2026, Genevieve Triplett
Recommended Citation
Triplett, G.(2026). How Are Serpentine and Non-Serpentine Populations of Mimulus Guttatus Maintained Despite Close Proximity?. (Master's thesis). Retrieved from https://scholarcommons.sc.edu/etd/8845