title: Sexual ornaments, body morphology, and swimming performance in naturally hybridizing swordtails (teleostei: xiphophorus).
abstract: 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.
authors.affiliation: Department of Biology, Texas A&M University, College Station, Texas, United States of America; Centro de Investigaciones Científicas de las Huastecas, Colonia Aguazarca, Calnali, Hidalgo, México.
authors.forename: James B
authors.initials: JB
authors.lastname: Johnson
authors.affiliation: Department of Biology, Texas A&M University, College Station, Texas, United States of America.
authors.forename: Danielle C
authors.initials: DC
authors.lastname: Macedo
authors.affiliation: Department of Biology, Texas A&M University, College Station, Texas, United States of America.
authors.forename: Courtney N
authors.initials: CN
authors.lastname: Passow
authors.affiliation: Department of Biology, Texas A&M University, College Station, Texas, United States of America; Centro de Investigaciones Científicas de las Huastecas, Colonia Aguazarca, Calnali, Hidalgo, México.
authors.forename: Gil G
authors.initials: GG
authors.lastname: Rosenthal
mesh_terms: D000818:Animals; D003532:Cyprinodontiformes / Q000502:physiology*; D008124:Locomotion / Q000502:physiology; D010641:Phenotype; D012726:Sexual Behavior, Animal / Q000502:physiology*; D013550:Swimming / Q000502:physiology*