To understand factors that shape emergent evolutionary radiations, community assembly, and the maintenance of diversity in changing landscapes, my work combines molecular and ecological population assessments of a novel plant-herbivore interaction. In this dissertation I examine how deterministic and stochastic factors shape ecological interactions and population structure in the Chinese tallow tree, Triadica sebifera, and a newly discovered herbivore in the invasive North American range, Caloptilia triadicae. Much is known about evolved variation in invasive Triadica populations, but the extent to which stochastic and deterministic factors shape post-invasion species interactions with Caloptilia, the only known specialist in North America, remains unclear in this and many other systems involving invasive species. To characterize how Triadica-Caloptila associations vary according to geography and host genetics, I conducted an observational field study, incorporating a range of genetically variable Triadica populations (intrinsic deterministic factors), climate (extrinsic deterministic factors), and isolation by distance (stochastic factors). I found that geography and genotypic variability in the tree explained the most variation in leaf toughness and caterpillar abundance. To confirm the role of host genetics on this interaction, I also conducted a common garden experiment to assess the role of geographically structured genetic variation of Triadica in shaping interactions with Caloptilia, while controlling for confounding climatic gradients and distance related stochastic processes. The common garden study reinforced the conclusion that intrinsic deterministic factors are important drivers shaping this interaction, but also revealed that seasonal changes mediate the relative impact of host genetics and microhabitat. Using measures of genetic variation, I also conducted molecular analyses to determine if the ecological patterns I observed in my field and common garden studies emerged as patterns of genetic structure between host and herbivore. The results of this study confirmed the primary role of geographic isolation, and a secondary role for host genetic identity, as drivers of herbivore population structure. Overall, this dissertation informs our current understanding of the role of host genetics, geographic isolation, microclimate and seasonality in shaping mosaics of species interactions. Additionally, this work expands our understanding of how these factors influence the applied conservation of habitats threatened by invasive plants and outbreaking novel herbivores. / 1 / Rebecca Frances Hazen
| Identifer | oai:union.ndltd.org:TULANE/oai:http://digitallibrary.tulane.edu/:tulane_46038 |
| Date | January 2015 |
| Contributors | Hazen, Rebecca F. (author), Blum, Michael (Thesis advisor), School of Science & Engineering Ecology and Evolutionary Biology (Degree granting institution) |
| Publisher | Tulane University |
| Source Sets | Tulane University |
| Language | English |
| Detected Language | English |
| Type | Text |
| Format | electronic |
| Rights | Embargo |
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