PARENT SESSION
Oral Session #70: Invasive Species: Aquatic.
Presiding: S. Juliano
Wednesday, August 7. 1:00 PM to 4:45 PM. Grand Ballroom East, Radisson.

Life histories, abiotic tolerances and population performance in Gambusia: a comparison of congeners of varying invasiveness.

Rehage, Jennifer^*,1, Fischer, Elizabeth¹, Sih, Andy², ¹ jsrehage@ucdavis.edu, Lexington, KY² University of California, Davis, CA

ABSTRACT- The role of species-specific traits in the invasion process is an issue of great interest in invasion biology. While the realized level of success of a non-indigenous species in a novel community is thought to be dependent on community traits and interactions between invader traits and community traits, certain key invader traits are generally expected to increase the probability of success of an invading species in any given community. Life histories and environmental tolerances have been suggested to be key in explaining and predicting the ability of a non-indigenous species to become abundant and spread in novel habitats. In this study, we compared the life history traits and cold temperature tolerances of four Gambusia species, the widespread and invasive sister species G. affinis and G. holbrooki and two restricted and noninvasive species, G. hispaniolae and G. geiseri. We then investigated whether differences in life histories and environmental tolerances measured in the lab translated to differences in the ability of these species to become and remain abundant in outdoor cattle tanks setup to simulate the invasion of a simplified temperate community. Our results indicate that the invasive Gambusia species exhibit a range of life history traits associated with higher population growth rates compared to the noninvasive species. Invasive Gambusia had larger broods of smaller offspring, higher juvenile growth rates, and consequently reached reproductive maturity sooner and at smaller sizes than noninvasives. We found evidence that the better life history performance of the invasive species did, in fact, translate to better population-level performance under standardized semi-field conditions. Invasive Gambusia achieved and maintained significantly greater population sizes than the noninvaders. We also found the invasive Gambusia species to be significantly more tolerant of colder temperatures than the noninvaders, which also had an effect on their ability to remain abundant and survive overwintering conditions.

KEY WORDS: invasion, life history, Gambusia , vertebrate