title: Why does offspring size affect performance? Integrating metabolic scaling with life-history theory.
abstract: Within species, larger offspring typically outperform smaller offspring. While the relationship between offspring size and performance is ubiquitous, the cause of this relationship remains elusive. By linking metabolic and life-history theory, we provide a general explanation for why larger offspring perform better than smaller offspring. Using high-throughput respirometry arrays, we link metabolic rate to offspring size in two species of marine bryozoan. We found that metabolism scales allometrically with offspring size in both species: while larger offspring use absolutely more energy than smaller offspring, larger offspring use proportionally less of their maternally derived energy throughout the dependent, non-feeding phase. The increased metabolic efficiency of larger offspring while dependent on maternal investment may explain offspring size effects-larger offspring reach nutritional independence (feed for themselves) with a higher proportion of energy relative to structure than smaller offspring. These findings offer a potentially universal explanation for why larger offspring tend to perform better than smaller offspring but studies on other taxa are needed.
authors.affiliation: School of Biological Sciences, Monash University, Melbourne, Victoria 3800, Australia amanda.pettersen@monash.edu.
authors.forename: Amanda K
authors.initials: AK
authors.lastname: Pettersen
authors.affiliation: School of Biological Sciences, University of Queensland, Brisbane, Queensland 4072, Australia.
authors.forename: Craig R
authors.initials: CR
authors.lastname: White
authors.affiliation: School of Biological Sciences, Monash University, Melbourne, Victoria 3800, Australia.
authors.forename: Dustin J
authors.initials: DJ
authors.lastname: Marshall
mesh_terms: D000818:Animals; D005075:Biological Evolution; D049628:Body Size; D002013:Bryozoa / Q000254:growth & development / Q000502:physiology*; D004734:Energy Metabolism; D007814:Larva / Q000254:growth & development / Q000502:physiology; D013045:Species Specificity
keywords: allometry; egg size; maternal effect