Sexual Ornaments, Body Morphology, and Swimming Performance in Naturally Hybridizing Swordtails (Teleostei: Xiphophorus) Academic Article uri icon


  • Determining the costs of sexual ornaments is complicated by the fact that ornaments are often integrated with other, non-sexual traits, making it difficult to dissect the effect of ornaments independent of other aspects of the phenotype. Hybridization can produce reduced phenotypic integration, allowing one to evaluate performance across a broad range of multivariate trait values. Here we assess the relationship between morphology and performance in the swordtails Xiphophorus malinche and X. birchmanni, two naturally-hybridizing fish species that differ extensively in non-sexual as well as sexual traits. We took advantage of novel trait variation in hybrids to determine if sexual ornaments incur a cost in terms of locomotor ability. For both fast-start and endurance swimming, hybrids performed at least as well as the two parental species. The sexually-dimorphic sword did not impair swimming performance per se. Rather, the sword negatively affected performance only when paired with a sub-optimal body shape. Studies seeking to quantify the costs of ornaments should consider that covariance with non-sexual traits may create the spurious appearance of costs.

altmetric score

  • 1

author list (cited authors)

  • Johnson, J. B., Macedo, D. C., Passow, C. N., & Rosenthal, G. G.

citation count

  • 8

publication date

  • October 2014