Department of Biology
Alistair J. Cullum and Albert F. Bennett
Department of Ecology and Evolutionary Biology
University of California, Irvine
Irvine, CA 92697-2525
American Zoologist, 35(5): 140A (1995)
1995 Annual Meeting of the American Society of Zoologists
Washington, D. C.
Abstract. Locomotor ability has often been perceived as important in the outcome of many predator-prey interactions. However, few studies have actually examined selection on locomotion within generations, and fewer if any have looked for genetic responses to predation pressure. Natural populations of guppies (Poecilia reticulata) in Trinidad provide a natural experimental system to examine the evolutionary effects of high vs. low predation intensities on two aspects of escape swimming. The first is the rapid (or "C") start, a hard-wired, turn-and-"kick" escape response to approaching shock waves; the second is the subsequent burst swimming used by the fish. Wild caught and lab-reared fish from replicate populations of high and low predation intensities were filmed using high-speed video while escape responses were elicited via a standardized stimulus. Video frames were digitized to yield data on velocities and distances moved during different phases of the escape response. Work to date suggests that rapid ("C") starts have not shown any evolutionary divergence between the two sorts of populations, but that subsequent burst swimming is faster in high-predation populations. This research was supported by NSF grants IBN 9118346 and IBN 9420155 to AFB.