Date Approved

8-2019

Graduate Degree Type

Thesis

Degree Name

Biology (M.S.)

Degree Program

Biology

First Advisor

Charlyn Partridge

Second Advisor

Jennifer Moore

Third Advisor

Timothy Evans

Academic Year

2018/2019

Abstract

Invasive species are a serious threat to biodiversity worldwide. While the impacts of invasive species increase annually, many gaps in our understanding of how these species invade, adapt, and thrive in the novel ecosystems into which they are introduced remain. This thesis aimed to add to our knowledge of invasion science, using the perennial forb Gypsophila paniculata as a study system. Gypsophila paniculata is a shrub native to the Eurasian steppe that was introduced into North America in the late 1800’s. After introduction, G. paniculata quickly spread and now occupies diverse ecosystems across N. America. In chapter II of this thesis, I assessed relationships among G. paniculata growing in seven locations across its introduced range and current invasion status using historical herbarium records. Genetic relationships were analyzed using microsatellite analyses, which suggested the presence of two genetic clusters; when herbarium records were grouped according to these clusters, two distinct expansion phases became visible, suggesting the presence of at least two invasion events. In chapter III, I analyzed two populations of G. paniculata growing in distinct environments (Chelan, Washington and Petoskey, Michigan) for phenotypic and gene expression differences that may confer potential adaptation to unique environmental stressors. Results revealed that seeds collected from Washington germinated significantly quicker than seeds collected in Michigan (pairwise logrank test, p < 0.0001). When grown in a common garden, seeds collected in Washington had higher levels of emergence (two-sided proportion test, p=0.00018). No significant differences in tissue allocation between populations were observed (ANOVA, p = 0.0645); however, family effects were visible (ANOVA, p=0.0301), though whether they are a function of maternal investment or evidence of genetic differences is unclear. Finally, results of RNA-seq transcriptome analyses revealed 1,149 genes differentially expressed among all tissue types (root, stem, and leaf); when considered according to tissue type and growing location, overrepresentations of genes related to circadian rhythm, stress responses, and nutrient deprivation were observed among the genes that were differentially expressed. These results not only add to our understanding of the North American invasion of Gypsophila paniculata, but also increase our understanding of how invasive species may be able to cope with the novel environments they encounter in their introduced range.

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