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

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第20214号 / 理博第4299号 / 新制||理||1617(附属図書館) / 京都大学大学院理学研究科生物科学専攻 / (主査)准教授 川北 篤, 教授 田村 実, 准教授 酒井 章子 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

L’objectif de ma thèse visait à étudier les processus évolutifs ayant conduit à l’évolution du mode de vie galligène et à rechercher des effecteurs impliqués dans l’induction des galles dans la famille des Gracillariidae (Lepidoptera) avec un accent particulier sur deux espèces, Borboryctis euryae et Caloptilia cecidophora. Nous avons ainsi démontré que ces deux espèces présentent la particularité de posséder un mode de vie intermédiaire entre mineur de feuille et inducteur de galle. Le tissu prolifératif présent dans la mine de B. euryae s’apparente en effet à une galle et les larves de C. cecidophora connaissent une transition du mode de vie mineur de feuille à galligène au cours de leur développement. Des campagnes de terrain ont permis de découvrir de nouvelles espèces de Caloptilia inductrices de galles, et leur étude phylogénétique a montré qu’elles forment un groupe monophylétique. Enfin, exploitant la transition de mode de vie de C. cecidophora ainsi que son contexte phylogénétique, nous avons appliqué une approche de transcriptomique comparative intra- et inter-espèce afin de rechercher des effecteurs candidats impliqués dans la formation de galle. / The aim of my thesis was to study the evolutionary processes that led to the evolution of the gall-inducing lifestyle and to look for effectors involved in the induction of galls in the Gracillariidae family (Lepidoptera) with a particular focus on two species, Borboryctis euryae and Caloptilia cecidophora. We have demonstrated that these two species have a particular intermediate life-style between leaf-miner and gall-inducer. The proliferative tissue in the B. euryae mine is similar to a gall and the larvae of C. cecidophora undergo a transition from leaf-miner to gall-inducer during their development. Field work has uncovered new gall-inducing Caloptilia species, and their phylogenetic study has shown that they form a monophyletic group. Finally, exploiting the transition of feeding habit of C. cecidophora as well as its phylogenetic context, we applied a comparative intra- and inter-species transcriptomic approach to search for candidate effectors involved in gall induction.

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