Hybridization and whole genome duplication as drivers of biological invasions

Autor: Mattingly, Kali Z.
Jazyk: angličtina
Rok vydání: 2021
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Druh dokumentu: Text
Popis: Humans engineer their environments by transporting species around the planet. In a new environment, most introduced species will perish, but a small proportion can become invasive, spreading widely and impacting their environments. My dissertation explores how evolutionary processes shape invasive species. I studied two mechanisms of invasive species evolution that can induce rapid evolutionary change: hybridization (mating between genetically distinct individuals) and whole genome duplication (WGD, when offspring inherit an extra set of chromosome pairs). In Chapters 1 and 2, I describe experiments with members of the model plant genus Arabidopsis differing only in genome size and status as either parent or hybrid, effectively isolating the independent effects of WGD and hybridization on traits. I grew plants together under controlled conditions and measured traits and phenotypic plasticity (the change in trait values across imposed environmental gradients). For the handful of traits and gradients in which WGD shifted plasticity values, WGD consistently increased plasticity (Chapter 1). This study provides the most controlled experimental evidence to date in support of the hypothesis that WGD increases plasticity, a hypothesis invoked to help explain how WGD has driven evolution. In contrast to WGD, I found that hybridization produced larger effects on both mean traits and plasticity (Chapter 2). This experiment is the first to fully isolate hybridization and WGD effects on plasticity.In nature, genetic and trait variation provide the raw material allowing invasive species to initially prevail in and, potentially, adapt to the introduced environment. I examined patterns of variation related to hybridization and WGD for two invasive plant systems (Chapters 3 and 4). Chapter 3 focuses on purple loosestrife (Lythrum salicaria), a well-studied species for which other authors have documented post-introduction changes in traits and genetics. A little-studied, more recently introduced horticultural species, European wand loosestrife (L. virgatum), can escape into the wild and is also thought to hybridize with already-established purple loosestrife. The two also differ in genome size: invasive-range L. salicaria is tetraploid and L. virgatum is diploid. I compared fitness and flooding tolerance in L. salicaria and virgatum. I found that both succeeded under inundation and produced aerenchyma, a specialized tissue that facilitates flooding tolerance. Lythrum virgatum produced more inflorescence biomass than L. salicaria, suggesting it may perform even better than L. salicaria under some conditions and should be regulated along with L. salicaria.From a landscape scale, patterns of evolution are captured as genetic and morphological variation among populations. Understanding similarities and differences across different regions can help us understand and predict paths of spread. In Chapter 4, I took this perspective to investigate lesser celandine (Ficaria verna) invasions in four metropolitan areas. Lesser celandine is also a horticultural species and has multiple subspecies that vary in ploidy. My genetic and morphological evidence pointed to widespread sexual reproduction in the introduced range. Both sexual and clonal reproduction have facilitated spread, and my resistance analyses indicated water dispersal and habitat availability as moderators of spread. Broadly, my work adds to the growing literature describing the evolution of introduced species.
Databáze: Networked Digital Library of Theses & Dissertations
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