title: As the sword grows: individual variation and ontogenetic effects of a sexually selected trait on locomotor performance in Xiphophorus hellerii.
abstract: Previous studies aimed at detecting costs of sexually selected traits have yielded mixed results partly because of variable methods. We present a novel approach: a repeated-measures design to examine individual variation in locomotor performance of male Xiphophorus hellerii as the sexually selected sword develops ontogenetically and to determine whether the growth of a sexually selected trait alters consistency of performance. Individual differences in sprint speed, critical swimming speed (stamina), and relative sword length were statistically repeatable over 9 wk. However, using the Akaike Information Criterion corrected for small sample sizes, the best-fit predictive models for swimming performance did not include sword length or relative sword length. Furthermore, in less supported models and within-week comparisons, there was no statistically significant effect of sword length on performance. These results suggest little effect of the sword on locomotor abilities, which is inconsistent with results from some previous experimental manipulations, possibly because compensatory traits develop ontogenetically in parallel with the sword. However, our results are consistent with correlational studies of natural variation that suggest no locomotor cost of the sword. These results do not necessarily imply a complete lack of a cost to the sword but rather lack of a functional cost for swimming performance.
authors.affiliation: Department of Biology, University of California, Riverside, California 92521, USA. ceoufiero@ucdavis.edu
authors.forename: Christopher E
authors.initials: CE
authors.lastname: Oufiero
authors.forename: Kristine
authors.initials: K
authors.lastname: Jugo
authors.forename: Paulina
authors.initials: P
authors.lastname: Tran
authors.forename: Theodore
authors.initials: T
authors.lastname: Garland
mesh_terms: D058500:Animal Fins / Q000033:anatomy & histology / Q000502:physiology*; D000818:Animals; D003532:Cyprinodontiformes / Q000033:anatomy & histology / Q000235:genetics / Q000502:physiology*; D008297:Male; D011897:Random Allocation; D012641:Selection, Genetic; D013550:Swimming / Q000502:physiology*