title: Repeatability of locomotor performance and morphology-locomotor performance relationships.
abstract: There is good evidence that natural selection drives the evolution of locomotor performance, but the processes that generate the among-individual variation for selection to act on are relatively poorly understood. We measured prolonged swimming performance, Ucrit, and morphology in a large cohort (n=461) of wild-type zebrafish (Danio rerio) at ∼6 months and again at ∼9 months. Using mixed-model analyses to estimate repeatability as the intraclass correlation coefficient, we determined that Ucritwas significantly repeatable (r=0.55; 95% CI: 0.45-0.64). Performance differences between the sexes (males 12% faster than females) and changes with age (decreasing 0.07% per day) both contributed to variation in Ucritand, therefore, the repeatability estimate. Accounting for mean differences between sexes within the model decreased the estimate of Ucritrepeatability to 21% below the naïve estimate, while fitting age in the models increased the estimate to 14% above the naïve estimate. Greater consideration of factors such as age and sex is therefore necessary for the interpretation of performance repeatability in wild populations. Body shape significantly predicted Ucritin both sexes in both assays, with the morphology-performance relationship significantly repeatable at the population level. However, morphology was more strongly predicative of performance in older fish, suggesting a change in the contribution of morphology relative to other factors such as physiology and behaviour. The morphology-performance relationship changed with age to a greater extent in males than females.
authors.affiliation: School of Biological Sciences, The University of Queensland, Brisbane, Queensland 4072, Australia.
authors.forename: Cara
authors.initials: C
authors.lastname: Conradsen
authors.affiliation: Department of Biological Sciences, University of Southern Maine, Portland, Maine 04103, USA.
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Walker
authors.affiliation: School of Biological Sciences, The University of Queensland, Brisbane, Queensland 4072, Australia.
authors.forename: Catherine
authors.initials: C
authors.lastname: Perna
authors.affiliation: School of Biological Sciences, The University of Queensland, Brisbane, Queensland 4072, Australia k.mcguigan1@uq.edu.au.
authors.forename: Katrina
authors.identifier: http://orcid.org/0000-0002-0525-2202
authors.initials: K
authors.lastname: McGuigan
keywords: Danio rerio; Mixed models; Ontogeny; Performance landscape; Prolonged swimming; Ucrit