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Competition among species for a discrete transient resource: instability leads to extinction.
Walters, Eric*,1, James, Frances1, 1 Florida State University, Tallahassee, FL
ABSTRACT- Shared resources often limit species assemblages. If the resource is discrete and transient, theory predicts that species richness will be maximized when the resource is used by different species at different stages of its transitory trajectory. We tested this hypothesis by examining the species assemblage associated with tree holes (a discrete transient resource) in pine forests of north Florida. Holes are recruited (excavated) by red-cockaded woodpeckers and competitively usurped to various degrees by the species in the assemblage throughout the hole's lifetime. Competitively dominant species are associated with earlier stages of transient resources. Indirect interactions among dominant species increased when one competitively dominant species was removed. Through transition models, we show that the assemblage is not stable. Most species in the assemblage will be lost over time. In experiments where the competitively dominant species was removed, time to extinction was decreased for most species, relative to controls. Our experiments show that species richness is not maximized in our system. More species compete for earlier stages of the transitory resource than later stages. Earlier stages tend to be associated with decreased levels of predation than compared with later stages. Our findings also suggest that a combination of an insufficient recruitment of resources concomitant with an increase in the competitively dominant species has led to instability in the assemblage, resulting in reduced species richness.
KEY WORDS: competition, assemblage