Age-dependent genetic variance in a life-history trait in the mute swan

• Published in: Proceedings of the Royal Society. B, Biological sciences Vol. 273; no. 1583; pp. 225 - 232
• Main Authors: Charmantier, Anne, Perrins, Christopher, McCleery, Robin H, Sheldon, Ben C
• Format: Journal Article
• Language: English
• Published: London The Royal Society 22.01.2006
• Subjects: Additive Genetic Variance; Age; Age structure; Age-Dependence; Aging - genetics; Animal Model; Animal models; Animals; Anseriformes - genetics; Anseriformes - growth & development; Breeding; Cygnus olor; Evolution; Female; Genetic variance; Genetic Variation; Heritability; Oviposition - genetics; Phenotype; Phenotypic traits; Quantitative genetics; Senescence; Statistical variance
• ISSN: 0962-8452; 1471-2954
• DOI: 10.1098/rspb.2005.3294

Genetic variance in characters under natural selection in natural populations determines the way those populations respond to that selection. Whether populations show temporal and/or spatial constancy in patterns of genetic variance and covariance is regularly considered, as this will determine whether selection responses are constant over space and time. Much less often considered is whether characters show differing amounts of genetic variance over the life-history of individuals. Such age-specific variation, if present, has important potential consequences for the force of natural selection and for understanding the causes of variation in quantitative characters. Using data from a long-term study of the mute swan Cygnus olor, we report the partitioning of phenotypic variance in timing of breeding (subject to strong natural selection) into component parts over 12 different age classes. We show that the additive genetic variance and heritability of this trait are strongly age-dependent, with higher additive genetic variance present in young and, particularly, old birds, but little evidence of any genetic variance for birds of intermediate ages. These results demonstrate that age can have a very important influence on the components of variation of characters in natural populations, and consequently that separate age classes cannot be assumed to be equivalent, either with respect to their evolutionary potential or response.