A TEST OF HYBRID GROWTH DISADVANTAGE IN WILD, FREE-RANGING SPECIES PAIRS OF THREESPINE STICKLEBACK (GASTEROSTEUS ACULEATUS) AND ITS IMPLICATIONS FOR ECOLOGICAL SPECIATION

Authors

  • Eric B. Taylor,

    1. Department of Zoology, Beaty Biodiversity Research Centre and Museum, and Native Fishes Research Group, University of British Columbia, 6270 University Blvd., Vancouver, British Columbia V6T 1Z4, Canada
    2. E-mail: etaylor@zoology.ubc.ca
    Search for more papers by this author
  • Carling Gerlinsky,

    1. Department of Zoology, Beaty Biodiversity Research Centre and Museum, and Native Fishes Research Group, University of British Columbia, 6270 University Blvd., Vancouver, British Columbia V6T 1Z4, Canada
    2. Fisheries Centre, Aquatic Ecosystems Research Laboratory, 2202 Main Mall, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
    Search for more papers by this author
  • Nicole Farrell,

    1. Department of Zoology, Beaty Biodiversity Research Centre and Museum, and Native Fishes Research Group, University of British Columbia, 6270 University Blvd., Vancouver, British Columbia V6T 1Z4, Canada
    Search for more papers by this author
  • Jennifer L. Gow

    1. Department of Zoology, Beaty Biodiversity Research Centre and Museum, and Native Fishes Research Group, University of British Columbia, 6270 University Blvd., Vancouver, British Columbia V6T 1Z4, Canada
    Search for more papers by this author

Abstract

Ecological speciation is the evolution of reproductive isolation as a direct or indirect consequence of divergent natural selection. Reduced performance of hybrids in nature is thought to be an important process by which natural selection can favor the evolution of assortative mating and drive speciation. Benthic and limnetic sympatric species of threespine stickleback (Gasterosteus aculeatus) are adapted to alternative trophic niches (bottom browsing vs. open water planktivory, respectively) and reduced feeding performance of hybrids is thought to have contributed to the evolution of reproductive isolation. We tested this “hybrid-disadvantage hypothesis” by inferring growth rates from otoliths sampled from wild, free-ranging benthic, limnetic, and hybrid sticklebacks in two lakes. There were significant differences in growth rate between lakes, life-history stages, and among years (maximum P = 0.02), as well as interactions between most factors, but not between hybrid and parental species sticklebacks in most comparisons. Our results provide little evidence of a growth disadvantage in hybrid sticklebacks when free-ranging in nature. Although trophic ecology per se may contribute less to ecological speciation than envisioned, it may act in concert with other aspects of stickleback biology, such as interactions with parasites, predators, competitors, and/or sexual selection, to present strong multifarious selection against hybrids.

Ancillary