Ecological Interactions in a Changing World

Abstract

21st-century ecology is necessarily a science of change. Understanding how and why communities and interacting species respond to transformations in global climate and human land use can help improve our ability to forecast and manage shifts in ecological interactions. In this dissertation, I present work that asks these kinds of questions as they relate to plants, insects, and their relationships. In chapter one I use a Bayesian hierarchical modeling approach to examine how fruiting and seed dispersal phenology is influenced by climate across the subalpine wildflower community on Mt. Rainier. I find that the kinds of changes we expect to occur in snowmelt timing, temperature, and soil moisture are likely to shorten the time it takes for plants to transition from flowering to seed dispersal. This work highlights the importance of increased attention on post-flowering phases of plant reproductive phenology, and suggests that the future may shift relationships between plants and their animal associates, including frugivores and invertebrate seed predators. In chapter two I ask how the interaction between an ecologically important species (subalpine lupine, Lupinus latifolius var. subalpinus) and its primary insect herbivore (the Cascade grasshopper, Prumnacris rainierensis) changes with elevation, and use a combination of observations, experiments, and trait measurements to tease apart the drivers of these patterns. The results of this chapter show that grasshopper herbivory has meaningful impacts on lupines, and that the strength of this relationship increases with elevation due to a complex suite of interactions between abiotic factors and plant and insect traits that influence levels of consumption. These findings point to the difficulty of predicting how species interactions will change in systems where warming is not the sole variable of interest and where climatic history shapes populations’ responses to environmental change. Finally, in chapter three I take a meta-analytic approach to test the hypothesis that ecological restoration is an effective means of invertebrate conservation, using a dataset comprising 59 studies of restoration impacts on invertebrate biodiversity with a wide geographic and taxonomic scope. On average, I find that the restoration of native vegetation is associated with significant increases in species richness, abundance, and diversity. However, high-among study heterogeneity suggests an urgent need for more research on neglected taxa, habitats, and geographic regions, more careful study design and reporting, and a move toward sharing raw data from restorations assessments. Overall, this work makes novel contributions to our knowledge about biotic responses to climate change from the perspective of plants and insects, and underscores the fundamental complexity of ecological dynamics.