The Role of Consumer Interactions in the Consequences and Causes of Community Phylogenetic Structure

Phylogenetic structure measures patterns of evolutionary history within communities – are some communities composed of species more distantly or closely related than expected by chance? Due to common descent, closely related species are more ecologically similar, and so degrees of relatedness in a community may be good predictors of its ecology, more so than the number of species. Whether we are speaking of how phylogenetic structure arises as a consequence of ecological processes, or how phylogenetic structure affects the functioning of communities, the role of consumer organisms has received less attention than the role of resources. In this thesis, I ask what are the consequences and causes of phylogenetic structure of a potentially multi-level community, focusing on the underappreciated effects of consumer-resource interactions. In Chapter 2, I show how phylogenetic diversity of plant communities predicts the diversity and abundance of arthropods captured in a long-running biodiversity experiment better than species richness alone. In Chapter 3, I show how phylogenetic diversity and species richness interact to explain herbivore damage at a whole community level. In Chapter 4, I explore how phylogenetic structure of old field plant communities differs in plots of contrasting disturbance history, and speculate as to what factors – such as herbivory – may have contributed to these differences. In Chapter 5, I present a model which incorporates competition – through both resources and consumers of a focal trophic level – and environmental filtering, two factors which are thought to impact phylogenetic structure through their influence on ecological similarity. I show that environmental filtering interacts with competition to determine the coexistence of similar species, and that consumers may have different effects than do resources. My dissertation provides new insight into the importance of consumers in ecological communities, both through their effect on, and through their response to, patterns of evolutionary history in their prey.Ph