Author ORCID Identifier

https://orcid.org/0000-0002-6023-5659

Defense Date

2026

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Integrative Life Sciences

First Advisor

Andrew J. Eckert

Second Advisor

Bret M. Boyd

Third Advisor

Laura F. Galloway

Fourth Advisor

Michael S. Rosenberg

Fifth Advisor

Rodney J. Dyer

Abstract

Plant mating systems are key determinants of fitness. Angiosperms exhibit a wide variety of reproductive strategies, including self-fertilization (or selfing), outcrossing, and mixed mating. It has been estimated that up to 43% of plant species are capable of selfing, and selfing has been hypothesized to provide reproductive assurance where opportunities for mating may be limited, such as in marginal environments. However, questions regarding the overall distribution of selfing rates across angiosperms, the maintenance of mixed mating in the face of inbreeding depression, and the impact of self-fertilization on diversification rates remain incompletely resolved. Here, we explore the dynamics of self-fertilization across three lines of inquiry: 1) addressing systematic bias toward the study of plant species capable of self-fertilization, 2) using phylogenetic state-dependent speciation-extinction models to assess the impact of mating and sexual system traits on rates of diversification through time, and 3) assessing if habitat marginality as measured by species distribution models can explain variation in selfing rate within populations. We present results demonstrating a bias favoring more “interesting” mating systems, yielding a bias against studies of outcrossing species, and also find that a limited number of families contribute disproportionately to the mating system literature. We also utilize state-dependent speciation-extinction models to examine how reproductive system traits like mating and sexual system impact diversification rates across a broadly distributed sample of 18 angiosperm families and discuss how these traits can be used together to improve our understanding of angiosperm reproductive dynamics. We find that mating systems do not help explain patterns of speciation and extinction on a phylogenetic tree, but that sexual systems often do. Finally, utilizing species distribution modeling, we discuss what drives population-level variation in selfing rates, and the potential implications of this for plants under a changing climate. We show that self-fertilization is more common in high-quality habitat, and that outcrossing may be more frequent in populations in poor habitat.

The overarching goal of this project was to better understand the evolutionary fate of self-fertilizing plants by attempting to resolve the apparent paradox presented by the observed frequency of selfing and mixed-mating strategies in nature with the negative evolutionary implications of self-fertilization. We first asked if this pattern could be explained by biased sampling causing an enrichment of selfing species in the scientific literature. While we did find that the data was biased, especially against the study of dioecious species, the magnitude of this bias is likely insufficient to explain the prevalence of selfing. Next, we investigated how selfing impacted diversification rates across different families and found that patterns of diversification were often better explained by sexual system rather than mating system, which suggests that mating system is not a singular predictor of evolutionary outcomes – but elevated rates of diversification associated with dioecy and monoecy suggest an advantage conferred by avoidance of selfing in some families. Finally, we discuss interactions between rates of selfing and the climate, a potential driver of by which variation in selfing rate might be maintained and find that habitat marginality may be a driver of observed differences in selfing rates for populations within a single species. Overall, this presents a picture consistent with opposing evolutionary pressures maintaining self-fertilization in some families, and a more nuanced view of the macroevolutionary patterns associated with self-fertilization, emphasizing the importance of understanding and incorporating both mating and sexual systems to yield a more complete picture of plant reproductive biology. Our work also illustrates both the challenges associated with quantifying biases in the scientific literature, and how this endeavor can be an important part of understanding difficult and long-standing biological questions and demonstrates the important role which multi-species and multi-family studies play in attempting to uncover generalizable macroevolutionary patterns.

Rights

© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

8-7-2026

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