Get access
Advertisement

Contrasting hybridization rates between sympatric three-spined sticklebacks highlight the fragility of reproductive barriers between evolutionarily young species

Authors

  • JENNIFER L. GOW,

    1. Department of Zoology, Biodiversity Research Centre and Native Fishes Research Group, University of British Columbia, 6270 University Boulevard, Vancouver, BC V6T 1Z4, Canada,
    Search for more papers by this author
  • CATHERINE L. PEICHEL,

    1. Division of Human Biology, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
    Search for more papers by this author
  • ERIC B. TAYLOR

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

J. L. Gow, Department of Zoology, University of British Columbia, 6270 University Boulevard, Vancouver, BC V6T 1Z4, Canada. Fax: 604 822 2416; E-mail: gow@zoology.ubc.ca

Abstract

Three-spined sticklebacks (Gasterosteus aculeatus) are a powerful evolutionary model system due to the rapid and repeated phenotypic divergence of freshwater forms from a marine ancestor throughout the Northern Hemisphere. Many of these recently derived populations are found in overlapping habitats, yet are reproductively isolated from each other. This scenario provides excellent opportunities to investigate the mechanisms driving speciation in natural populations. Genetically distinguishing between such recently derived species, however, can create difficulties in exploring the ecological and genetic factors defining species boundaries, an essential component to our understanding of speciation. We overcame these limitations and increased the power of analyses by selecting highly discriminatory markers from the battery of genetic markers now available. Using species diagnostic molecular profiles, we quantified levels of hybridization and introgression within three sympatric species pairs of three-spined stickleback. Sticklebacks within Priest and Paxton lakes exhibit a low level of natural hybridization and provide support for the role of reinforcement in maintaining distinct species in sympatry. In contrast, our study provides further evidence for a continued breakdown of the Enos Lake species pair into a hybrid swarm, with biased introgression of the ‘limnetic’ species into that of the ‘benthic’; a situation that highlights the delicate balance between persistence and breakdown of reproductive barriers between young species. A similar strategy utilizing the stickleback microsatellite resource can also be applied to answer an array of biological questions in other species’ pair systems in this geographically widespread and phenotypically diverse model organism.

Get access to the full text of this article

Ancillary