Browsing by Subject "genetic variation"
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Item The hidden costs of rapid adaptation: experimentally assessing the effects of standing variation on the pace and trajectory of evolution(2022-03) Griffin, JosieAs the planet changes at an alarming rate, there is a great need to understand why some populations are better equipped to rapidly adapt to their new environment than others. Many factors contribute, but populations are ultimately limited in their pace by their genetic makeup—they either have variants that allow them to survive or they do not. But, in the race to adapt, all sources of variation are not equal, and standing genetic variation is theorized to be of the most benefit in contributing to rapid adaptation. Here I explore the role of standing variation, both in a population’s ability to adapt at a rapid pace and in the potential long term evolutionary consequences that occur as a result. My work confirms expectations that increased standing variation in a population allows for a faster rate of adaptation, but although these populations are able to succeed in the short term, but this achievement comes at a significant cost to long term viability. All populations, across all experiments, that utilize standing variation as the genetic basis for rapid adaptation lose the ability to undergo sexual recombination, and therefore lose an important mechanism for maintaining variation in the long term. I begin by determining how the amount of standing variation present in a population correlates to the timing and rate of a successful adaptive response to a stressful environment. I assess how this result is intertwined with loss of sex and explore the mechanism for that loss. Then, I explore how the dynamics of the system change if the environmental shift occurs gradually rather than as a dramatic climactic event. Finally, I compare the variety of evolutionary strategies that develop in populations that began with standing variation versus mutation as their genetic substrate and evaluate their potential for success in the long term. Taken together, these results present a different picture of the role of standing variation than might be assumed. It does indeed allow for rapid adaptation, but the increased degree of genetic variation is not an evolutionary panacea and may send populations down evolutionary trajectories that are short-sighted.Item Human Impacts on Minnesota Prairie Genetics: Salted Environments, Echinacea Hybrids, and Local Seed Sourcing(2018-12) Goldsmith, NicholasHumans are modifying various aspects of the environment, from building roadways, to moving species beyond their range, to purposefully reconstructing plant communities. These actions affect both the current distribution of populations and the potential for populations to persist. In this dissertation, I examine two human-caused impacts to plant populations and one aspect of efforts to support native plant communities. In chapter one, I focus on the impact of sodium chloride, a road de-icing agent. Such agents can damage plants and change dominant species along roadsides. I carried out two experiments, planting a pedigreed population of the native prairie legume Chamaecrista fasciculata into a roadside environment and into four greenhouse salinity treatments. I tracked their survival and reproduction. Using Aster models, I detected potential to adapt both to roadside salinity and to low salinity in the greenhouse. I also detected gene-by-environment interactions in both experiments. These results indicate a potential to adapt, but a potential which may be slowed by gene-by-environment interactions. In chapter two, I focus on the interaction of Echinacea pallida, introduced outside of its range, on local populations of E. angustifolia. I used controlled crosses and monitored their seed set and the survival of the progeny over five years. Crossing of the two species produces offspring capable of surviving multiple years. Comparing conspecific and heterospecific crosses, I found that conspecific crosses of E. angustifolia resulted in lower pollen compatibility and survival to year four than did conspecific crosses with E. pallida or heterospecific crosses. These results demonstrate a risk to E. angustifolia populations by E. pallida populations planted nearby. In chapter three, I focus on efforts to remediate human impacts through restoration of Minnesota prairie plant communities, which depends on the production and use of source-identified seeds. Restoration practice often emphasizes use of seeds sourced from populations near the restoration site, but demand frequently outstrips supply. I conducted focus group interviews with groups of producers and users of locally-sourced seeds to identify strengths and weaknesses with current practices. Participants discussed continued increases in production and use of these plant materials but also identified aspects where improvement is needed.