Document: JEN-3-84-9

Feeding preferences of invasive vs. noninvasive Gambusia species.

REHAGE, J.*, A.SIH, B.BARNETT and E.MAURER

University of Kentucky, Lexington, KY 40506 USA ¹

Abstract:
A central question in the study of biological invasions is: What are the key ecological, genetic, life-history, and behavioral traits that characterize successful invaders? While there are hypotheses on traits that one might expect in successful invaders, few studies have tested these hypotheses. Studying closely related and morphologically similar taxa allows one to identify traits associated with invasions. A good system is the poeciliid fish, Gambusia, where the differences in geographic range and invasive ability are extreme. Gambusia affinis and Gambusia holbrooki (mosquitofish) have widespread distributions and have been successfully introduced for mosquito control in every continent except Antarctica. In contrast, other Gambusia are extremely restricted in range, including five U.S. species with protected status and two species now considered extinct. Behavioral traits might be a critical component of invasion success. Behavioral plasticity should be an important attribute of successful invaders when confronted with novel environments or novel prey. In this study, I focus on feeding behavior, a hypothesized key behavioral trait that may explain variation in invasive ability in this genus. I compare feeding preferences of four species: The widespread and invasive sister species G. affinis and G. holbrooki (mosquitofish), and two restricted species, G. geiseri and G. hispaniolae . G. geiseri is native to the two largest springs in Texas, and it is the only Texan endemic Gambusia species without protected status. G. hispaniolae is native to the Dominican Republic in the island of Hispaniola. Three prey types were used in this experiment, a surface (vestigial winged Drosophila ), a pelagic (Daphnia) , and a benthic (the isopod, Lirceus fontinalis ) prey. Encounter rates, attack rates, capture success, and feeding rates were quantified for each prey type from videotaped feeding trials. I tested the hypotheses that invasive species should be less choosy in their diets and should have higher feeding rates across the three prey types. Some of the results fit these hypotheses well, while surprisingly others do not.

Keywords: Biological invasions, feeding behavior, invasive species, Gambusia

This abstract is being presented at: 2:00 PM in session:
Oral Session #62: Freshwater Fish Ecology.