Author

Sarah R. Supp

Date of Award:

5-2013

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Biology

Advisor/Chair:

S. K. Morgan Ernest

Abstract

Biodiversity research aims to understand and predict the occurrence, abundance, and distribution of species and the diversity of species traits, body sizes, and functional roles in a community. Ecologists lack a comprehensive understanding of the interplay between processes driving biodiversity at differing spatiotemporal scales, hindering the ability to predict response to change. A crucial challenge facing ecologists is to incorporate knowledge of the regional dynamics and temporal stability of communities in biodiversity research. This dissertation investigates the role that species traits and system-level properties play in determining biodiversity at local sites and evaluates biodiversity response to change.

Local and regional processes may regulate biodiversity via their different influences on core (common, temporally persistent) and transient (rare, temporally intermittent) species. In Chapter 2, we tested the hypothesis that core vs. transient species have fundamentally different life-history traits that are associated with survival strategies targeted at local vs. regional habitat use. Using long-term mark-recapture data from a rodent community, we found that core species generally had high ecological specialization, high survival, low dispersal rates, and low reproductive effort compared to transient species. Life-history trade-offs may correspond to differing roles in maintaining species richness and responses to environmental change.

Macroecology describes patterns of biodiversity in communities without respect to species identities or traits. Diversity patterns (i.e., species-abundance distribution-SAD, species-area relationship-SAR, species-time relationship-STR) are well-studied, but drivers of these patterns are poorly understood. In Chapter 3, we tested the hypothesis that local-scale interactions influence the form of SADs, SARs, and STRs using long-term data from annual plant communities. Our results suggest that patterns are directly influenced by system-level properties (species richness, total abundance) and respond indirectly to local-scale processes. In Chapter 4, we analyzed data from a global-span database and found the SAD and species richness generally resilient to environmental change.

This work suggests that local processes are important determinants of species composition and abundance and may set an upper limit to species richness, but that regional processes are responsible for maintaining richness and community structure. This insight may partially explain why many biodiversity metrics are often invariant under environmental change scenarios.

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