title: The nature of nurture in a wild mammal's fitness.
abstract: Genetic variation in fitness is required for the adaptive evolution of any trait but natural selection is thought to erode genetic variance in fitness. This paradox has motivated the search for mechanisms that might maintain a population's adaptive potential. Mothers make many contributions to the attributes of their developing offspring and these maternal effects can influence responses to natural selection if maternal effects are themselves heritable. Maternal genetic effects (MGEs) on fitness might, therefore, represent an underappreciated source of adaptive potential in wild populations. Here we used two decades of data from a pedigreed wild population of North American red squirrels to show that MGEs on offspring fitness increased the population's evolvability by over two orders of magnitude relative to expectations from direct genetic effects alone. MGEs are predicted to maintain more variation than direct genetic effects in the face of selection, but we also found evidence of maternal effect trade-offs. Mothers that raised high-fitness offspring in one environment raised low-fitness offspring in another environment. Such a fitness trade-off is expected to maintain maternal genetic variation in fitness, which provided additional capacity for adaptive evolution beyond that provided by direct genetic effects on fitness.
authors.affiliation: Department of Integrative Biology, University of Guelph, Guelph, Ontario, Canada N1G 2W1 eryn.mcfarlane@gmail.com.
authors.forename: S Eryn
authors.initials: SE
authors.lastname: McFarlane
authors.affiliation: Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E9.
authors.forename: Jamieson C
authors.initials: JC
authors.lastname: Gorrell
authors.affiliation: Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E9.
authors.forename: David W
authors.initials: DW
authors.lastname: Coltman
authors.affiliation: Department of Natural Resource Sciences, McGill University, Macdonald Campus, Ste-Anne-de-Bellevue, Québec, Canada H9X 3V9.
authors.forename: Murray M
authors.initials: MM
authors.lastname: Humphries
authors.affiliation: Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E9.
authors.forename: Stan
authors.initials: S
authors.lastname: Boutin
authors.affiliation: Department of Integrative Biology, University of Guelph, Guelph, Ontario, Canada N1G 2W1.
authors.forename: Andrew G
authors.initials: AG
authors.lastname: McAdam
mesh_terms: D000818:Animals; D005260:Female; D056084:Genetic Fitness; D014644:Genetic Variation; D012098:Reproduction; D012589:Sciuridae / Q000235:genetics / Q000502:physiology*; D015874:Yukon Territory
keywords: Robertson-price identity; evolvability; fitness; maternal genetic effects
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