Get access

Reduction of sexual dimorphism in stream-resident forms of three-spined stickleback Gasterosteus aculeatus

Authors

  • J. Kitano,

    Corresponding author
    1. Department of Ecology and Evolutionary Biology, Graduate School of Life Sciences, Tohoku University, Sendai, Miyagi 980-8578, Japan
    2. PRESTO, Japan Science and Technology Agency, Honcho Kawaguchi, Saitama 332-0012, Japan
    3. Ecological Genetics Laboratory, Center for Frontier Research, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan
      Tel.: +81 55 981 9415; email: jkitano@lab.nig.ac.jp
    Search for more papers by this author
  • S. Mori,

    1. Biological Laboratory, Gifu-keizai University, Ogaki, Gifu 503-8550, Japan
    Search for more papers by this author
  • C. L. Peichel

    1. Division of Human Biology, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, U.S.A.
    Search for more papers by this author

Tel.: +81 55 981 9415; email: jkitano@lab.nig.ac.jp

Abstract

Sexual dimorphism in geometric body shape and external morphology was compared between marine and stream-resident forms of three-spined stickleback Gasterosteus aculeatus collected from North America and Japan. Some aspects of sexual dimorphism were shared between ecotypes: males had larger heads than females with no significant effect of ecotype on the magnitude of sexual dimorphism. By contrast, a significant sex-by-ecotype interaction was found for body depth. Males tended to have deeper bodies than females in both forms, but the magnitude of sexual dimorphism was reduced in stream-resident forms. Although females were generally larger in standard length and had larger pelvic girdles, significant sexual dimorphism in these traits was not consistently found across populations or ecotypes. These results suggest that some aspects of sexual dimorphism were shared between ecotypes, while others were unique to each population. The results further suggest that ecology may influence the evolution of sexual dimorphism in some external morphological traits, such as body depth.

Get access to the full text of this article

Ancillary