Doctoral Dissertations

Date of Award

5-1997

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Zoology

Major Professor

Sturat L. Pimm

Committee Members

James A. Drake, John L. Gittleman, Michael McKinney

Abstract

Ecological communities do not simply spring into existence. Rather, they are built through the addition and subtraction of species through time. This process, sometimes called community assembly, is an intrinsically complex event. This dissertation explores three aspects of this process. The first is the importance of interspecific competition in determining community membership. Through the use of introduced passeriforms on oceanic islands we uncovered two patterns consistent with the competition hypothesis: morphological overdispersion and a priority effect. Each pattern was found among the introduced passeriforms on the island of Saint Helena. In addition, we reviewed the evidence for similar pattern among the passeriforms on the islands of Oahu, Bermuda and Tahiti. We found good evidence to believe competition can play a deciding role in community membership among each island assemblage. The second aspect of assembly explored here was the influence of invasion rate on community structure and dynamics. Communities which are confronted with potential colonizing species sequentially reach stable, persistent endpoints. Those that are faced with groups of invaders chum through species regularly and quickly and never reach a persistent composition. Thus, invasion rate has profound influences on the resultant dynamics of the assembly process. Finally, we explored the implications of assembly theory to ecological restoration. Two aspects of restoration - achieving persistence and the appropriate species composition - can be directly translated into the lexicon of assembly theory. Using these two common points, we built a criteria for success. According to this criteria, only a very few restorations are considered completely restored. Most restoration are successfully returning a few ecosystem functions and sub-sets of the desired species composition. This discrepancy in results are placed within the context of assembly theory and alternative approaches to the art of restoration are discussed.

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