The evolution of offspring size: a metabolic scaling perspective

Pettersen, A. K., Schuster, L. and Metcalfe, N. B., (2022) The evolution of offspring size: a metabolic scaling perspective. Integrative and Comparative Biology, 62(5), pp. 1492-1502. (doi: 10.1093/icb/icac076) (PMID:35657724)

Abstract

Size at the start of life reflects the initial per offspring parental investment – including both the embryo and the nutrients supplied to it. Initial offspring size can vary substantially both within and among species. Within species, increasing offspring size can enhance growth, reproduction, competitive ability, and reduce susceptibility to predation and starvation later in life, that can ultimately increase fitness. Previous work has suggested that the fitness benefits of larger offspring size may be driven by energy expenditure during development – or how offspring metabolic rate scales with offspring size. Despite the importance of early life energy expenditure in shaping later life fitness trajectories, consideration of among-species scaling of metabolic rate at the time of birth as a potential source of general metabolic scaling patterns has been overlooked by theory. Here we review the patterns and processes of energy expenditure at the start of life when mortality is often greatest. We compile existing data on metabolic rate and offspring size for 191 ectotherm species spanning eight phyla and use phylogenetically-controlled methods to quantify among-species scaling patterns. Across a 109-fold mass range, we find that offspring metabolic rate scales hypometrically with size, with an overall scaling exponent of 0.66. This exponent varies across ontogenetic stage and feeding activity, but is consistently hypometric, including across environmental temperatures. Despite differences in parental investment, life history and habitat, large-offspring species use relatively less energy as a proportion of size, compared with small-offspring species. Greater residual energy can be used to fuel the next stages of life, particularly in low resource environments. Based on available evidence, we conclude that, while large knowledge gaps remain, the evolution of offspring size is likely shaped by context-dependent selection acting on correlated traits, including metabolic rates maintaining hypometric scaling, that operates within broader physical constraints.

• Item Type: Articles
• Additional Information: This work was supported by a Marie Skłodowska-Curie Actions Individual Fellowship grant [grant number 101022401 to A.K.P.].
• Keywords: Egg, embryo, energy, larvae, respiration, parental investment.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Metcalfe, Professor Neil
• Authors: Pettersen, A. K., Schuster, L., and Metcalfe, N. B.,
• College/School: College of Medical Veterinary and Life Sciences > School of Biodiversity, One Health & Veterinary Medicine
• Journal Name: Integrative and Comparative Biology
• Publisher: Oxford University Press
• ISSN: 1540-7063
• ISSN (Online): 1557-7023
• Published Online: 03 June 2022
• Copyright Holders: Copyright © 2022 The Authors
• First Published: First published in Integrative and Comparative Biology 62(5): 1492-1502
• Publisher Policy: Reproduced under a Creative Commons License

Project Code	Award No	Project Name	Principal Investigator	Funder's Name	Funder Ref	Lead Dept
312377		MITOCHADAPT	Neil Metcalfe	European Commission (EC)	101022401	Institute of Biodiversity, Animal Health and Comparative Medicine