Trade-off between steady and unsteady swimming underlies predator-driven divergence in Gambusia affinis

J Evol Biol. 2009 May;22(5):1057-75. doi: 10.1111/j.1420-9101.2009.01716.x.


Differences in predation intensity experienced by organisms can lead to divergent natural selection, driving evolutionary change. Western mosquitofish (Gambusia affinis) exhibit larger caudal regions and higher burst-swimming capabilities when coexisting with higher densities of predatory fish. It is hypothesized that a trade-off between steady (constant-speed cruising; important for acquiring resources) and unsteady (rapid bursts and turns; important for escaping predators) locomotion, combined with divergent selection on locomotor performance (favouring steady swimming in high-competition scenarios of low-predation environments, but unsteady swimming in high-predation localities) has caused such phenotypic divergence. Here, I found that morphological differences had a strong genetic basis, and low-predation fish required less hydromechanical power during steady swimming, leading to increased endurance. I further found individual-level support for cause-and-effect relationships between morphology, swimming kinematics and endurance. Results indicate that mosquitofish populations inhabiting low-predation environments have evolved increased steady-swimming abilities via stiffer bodies, larger anterior body/head regions, smaller caudal regions and greater three-dimensional streamlining.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Adaptation, Biological / physiology*
  • Analysis of Variance
  • Animals
  • Biomechanical Phenomena
  • Body Weights and Measures
  • Cyprinodontiformes / physiology*
  • Multivariate Analysis
  • Physical Endurance / physiology*
  • Predatory Behavior / physiology
  • Selection, Genetic*
  • Swimming / physiology*
  • Tail / anatomy & histology