UC Berkeley

This dissertation explores how climate shapes plant biogeography, and the implications for plant vulnerability in the face of ongoing climate change. Climate structures plant biodiversity patterns across biotic scales ranging from genes to species to biomes, not only by influencing plant physiology and its many downstream effects, but also by influencing plant movement through the transport of seeds, pollen, and spores by wind. Understanding these phenomena is a core goal in plant ecology, and has become an increasingly urgent societal priority as accelerating anthropogenic climate change threatens biodiversity and ecosystem services across the world. Focusing on large spatial scales, this dissertation research investigates three connected facets of climate biogeography. The three chapters proceed down a hierarchy of concepts, each focusing more narrowly and deeply on one aspect of the preceding chapter; the focal level of biotic organization narrows in tandem, beginning with a study of vegetation formations in the first chapter and ending with an analysis of genetic loci in the third. Chapter 1 begins broadly, developing a framework for integrating three previously separate paradigms of ecological vulnerability to climate change, and using this framework in a large-scale spatial analysis of vegetation vulnerability across the western US. Chapter 2 focuses on one of these three paradigms, spatial novelty, which addresses dispersal limitation under climate change. Many plant species disperse by wind, and this new conceptual and modeling work provides the first global assessment of how wind patterns may shape range shifts and gene flow as climate warms. In chapter 3, this focus on wind dispersal is further narrowed to an investigation of wind’s role in shaping landscape genetic patterns in trees. This study reanalyzes population genetic data from more than a hundred tree species worldwide using the wind connectivity models developed in chapter 2, and shows for the first time that wind shapes directional gene flow, genetic differentiation, and genetic diversity. In sum, these analyses each advance our understanding of how climate influences basic spatial ecology, while also developing concepts and tools that may help land managers and conservation practitioners hone strategies for adaptation to global environmental change.