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Reproductive versatility of plants is an important part of their success. We investigated environmental factors that influence the reproductive strategies of three non-native plants and investigate the larger impact of these factors at the population level. Initial work consisted of two studies with Trifolium repens. A two month experiment was conducted under a factorial design, testing a combination of resource abundance and heterogeneity. Resource distribution had no effect on reproductive strategy. Resource abundance increased the amount of biomass allocated to horizontal stem development and foraging, but showed no effect on flowering at two months. A four month study showed that fertilizer does increase inflorescence development. The conflict between the two studies is evidence that reproductive strategy and flowering cues in Trifolium repens are strongly influenced by density depended effects. Two studies were performed with Ailanthus altissma, a high impact invasive tree species. A germination study was conducted on seeds from Ailanthus altissima based on human land use legacy, in the form of brownfield and non-brownfield sites. Brownfield sites showed a significant reduction in seed germination, this difference in germination was independent of initial seed mass. These two factors indicate that individuals from a brownfield site have a reduced fitness benefit for the same amount of resources invested in seeds. Population genetics of Ailanthus altissima were surveyed across six sites, using a set of eight microsatellite loci. Despite a strong propensity for clonal growth, the microsatellites revealed no evidence of clonal reproduction at the population level. Geneflow between sites was found to be independent of geographic distance, rather, geneflow was linked to the level of human traffic at a site. Evidence was also found that land management practices were effective at inhibiting geneflow into managed sites. Finally, an investigation was conducted into the possibility of ecotypes and reproductive isolation in Schismus arabicus in the Sonoran and Mojave deserts, based on the extreme heterogeneity of the nurse plant dominated landscape. Results from the ITS marker showed no evidence of ecotypes at either site. Number of SNPs between individuals were not correlated with distance, indicating that high internal geneflow prevents the level of isolation necessary for the formation of ecotypes. MCMC modeling also showed a small, but consistent, unidirectional geneflow from the Mojave to the Sonoran desert site. This was taken as evidence of anthropogenic geneflow. Ultimately, it is shown that reproductive strategy and population structure are strongly influenced by anthropogenic factors such as nutrient level, land-use legacy, management practices, and anthropogenic transport.

ETD_7675

Ph.D.

Includes bibliographical references

by Anthony Brusa

doi:10.7282/T3377C2J

ETD doctoral

The author owns the copyright to this work.