Year of Publication

2003

Document Type

Dissertation

College

Arts and Sciences

Department

Biology

First Advisor

Andrew Sih

Abstract

Due to the irreversible nature of biological invasions, prediction has been a key area of emphasis in invasion biology. Specifically, the degree to which species-specific traits may help us predict invasion success is a core issue in the field. My research examined a series of traits and asked whether they were good predictors of invasion success, particularly establishment success. I compared traits among four species of the poeciliid fish Gambusia, two of them highly invasive (G. affinis and G. holbrooki) and two of them non-invasive (G. hispaniolae and G. geiseri).I examined abiotic tolerances, feeding behavior, behavioral responses to novel predation and competition, life histories, and dispersal tendencies. I found the invasive Gambusia species to be more tolerant of low temperatures and to exhibit higher feeding rates and dispersal tendencies than non-invasives. Invasive species were more likely to respond appropriately to novel predation by reducing foraging and activity level and by increasing refuge use, and less likely to show lower foraging success when faced with competitors. Invasives exhibited higher fecundity and juvenile growth rates, and consequently reached maturity sooner than non-invasives. I found no differences in the species' diet breadth or aggressiveness.I then simulated the invasions of simplified pond communities and measured establishment success (with and without novel competitors) and community impact by tracking population trajectories over several months. As predicted from the trait comparisons, I found that in both simulations invasive Gambusia outperformed non-invasives by achieving andvmaintaining larger populations. In the first experiment, only invasive Gambusia were able to successfully establish (non-invasive populations had zero survival). In the second experiment, invasive Gambusia populations were better able to cope with competition and had greater community impact on lower trophic levels than the non-invasives.Overall, species traits were good predictors of establishment success. A species' ability to cope with the abiotic conditions of the invaded community seemed particularly important to whether or not establishment occurred in the study communities. Life history traits and the species' ability to cope with biotic interactions were important to determining the level of establishment species achieved if invaders survived the novel abiotic element.

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