UC Santa Cruz

Recent research highlights the prevalence of intraspecific trait variation, even in relatively open ocean habitats. The ecological importance of intraspecific trait variation, however, while shown in freshwater and terrestrial ecosystems, remains unexplored in marine systems. While climates change rapidly and differentially across marine environments at scales within species ranges, population-level trait variation in response to abiotic drivers is inevitable. It is therefore timely and important to explore the climate drivers of intraspecific trait changes and their ecological consequences in marine systems. In this dissertation, I explore these dynamics in a model predator-prey system. The predators, Nucella ostrina-emarginata dogwhelks, exhibit low population connectivity and gene flow due to their life history. The prey, Mytilus californianus, the California mussel, is a foundational mussel that supports high intertidal diversity. These species exist throughout a mosaic of climate conditions in the California Current System, setting the stage for local scale climate effects on Nucella predation that have community consequences. In Chapter 1, I examine climate drivers of population-level variation in size selectivity of Nucella on Mytilus. I find that abiotic variables such as temperature and pH are the strongest drivers of Nucella prey size selectivity rather than neutral genetic relationships among populations, which have no effect. In Chapter 2, I test for population-level differences in the responses to acute exposure to acidified seawater on Nucella size selectivity and consumption time. I find that populations are affected differently by acidification, showing that climate change can affect Nucella predation on local scales. In Chapter 3, I test for community effects of population-level differences in Nucella predation on mussel beds in the field. I find that Nucella predation affects mussel bed size structure and in turn, size structure affects community composition, showing differential predation on a foundation species can alter communities. My dissertation links climate change, trait variation, and community ecology, demonstrating how climate can indirectly alter communities by shaping predator traits on local scales, and expanding the study of population-level trait variation into marine ecosystems.