Towards Understanding the Mechanism Maintaining a Stable Trichome Dimorphism in the Sacred Datura Plant (datura Wrightii)
- ISBN-10
- ISBN-13
- 9798698541295
- Category
- Datura wrightii
- Pages
- 117
- Language
- English
- Published
- 2020
- Author
- Jay Keche Goldberg
Description
The hairs of plants, known as trichomes, are the first line of defense against hungry herbivores. Trichomes are categorized into two different families: glandular (which produce and secrete a blend of secondary metabolites) and non-glandular (which lack secretory structures). Trichomes are highly variable across plant species, with some plant clades having multiple independent origins for glandular trichomes. Trichomes can also exhibit a large degree of intra-specific variation with multiple trichome morphs coexisting within populations. One such species with a trichome dimorphism is Datura wrightii, which has a sticky morph that produces glandular trichomes and a velvety morph that produces non-glandular trichomes exclusively. These two trichome morphs have coexisted in D. wrightii populations across the state of California for decades, yet the evolutionary and ecological mechanisms that maintain this stable dimorphism have not been elucidated. In this dissertation I investigate three non-mutually exclusive mechanisms that could be acting on the D. wrightiii dimorphism: negative frequency-dependent selection, associational effects, and asymmetric benefits from the predators of herbivores. Using a state-wide, field-based observational approach, I was able to show that changes in the frequency of the two morphs over a 20-year period correspond to the predictions of negative frequency-dependent selection, but that within-population associational effects may not underlie this selection regime. In my final chapter I show that a species of predatory lizard responds to a glandular trichome-derived component of herbivore odor, thereby suggesting that the sticky D. wrightii morph may be more attractive to the natural enemies of herbivores than the velvety morph.
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