Term of Award

Spring 1993

Degree Name

Master of Science in Biology

Document Type and Release Option

Thesis (restricted to Georgia Southern)


Department of Biology

Committee Chair

Michael P. Moulton

Committee Member 1

Denson K. McLain

Committee Member 2

John W. Parrish


The patterns of extinction were examined among species of passeriforms introduced to three oceanic islands (Oahu, Tahiti, and Bermuda). Survival was significantly greater for plumage monomorphic than plumage dimorphic species on Oahu and Tahiti. Bermuda did not show this pattern, possibly due to introduced species pool size. Previous studies have documented morphological overdispersion among surviving species and have shown that species introduced earlier are more likely to persist. Yet, neither morphological similarity nor introduction order differed significantly between plumage monomorphic and dimorphic species introduced on Oahu and Tahiti.

Also the abundance data were examined on Oahu in order to determine if monomorphic species had larger population sizes than the population sizes of dimorphic species. The abundance of the monomorphic species was not significantly different than the dimorphic species.

I suggest that plumage dimorphic species have experienced more intense sexual selection pressures, and that response to sexual selection in these species has contrained response to natural selection pressures, thereby, increasing the risk of extinction.


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