title: Indirect genetic effects underlie oxygen-limited thermal tolerance within a coastal population of chinook salmon.
abstract: With global temperatures projected to surpass the limits of thermal tolerance for many species, evaluating the heritable variation underlying thermal tolerance is critical for understanding the potential for adaptation to climate change. We examined the evolutionary potential of thermal tolerance within a population of chinook salmon (Oncorhynchus tshawytscha) by conducting a full-factorial breeding design and measuring the thermal performance of cardiac function and the critical thermal maximum (CTmax) of offspring from each family. Additive genetic variation in offspring phenotype was mostly negligible, although these direct genetic effects explained 53% of the variation in resting heart rate (fH). Conversely, maternal effects had a significant influence on resting fH, scope for fH, cardiac arrhythmia temperature and CTmax. These maternal effects were associated with egg size, as indicated by strong relationships between the mean egg diameter of mothers and offspring thermal tolerance. Because egg size can be highly heritable in chinook salmon, our finding indicates that the maternal effects of egg size constitute an indirect genetic effect contributing to thermal tolerance. Such indirect genetic effects could accelerate evolutionary responses to the selection imposed by rising temperatures and could contribute to the population-specific thermal tolerance that has recently been uncovered among Pacific salmon populations.
authors.affiliation: Department of Biology, University of Western Ontario, London, Ontario, Canada.
authors.forename: Nicolas J
authors.initials: NJ
authors.lastname: Muñoz
authors.affiliation: Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Katja
authors.initials: K
authors.lastname: Anttila
authors.affiliation: Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Zhongqi
authors.initials: Z
authors.lastname: Chen
authors.affiliation: Yellow Island Aquaculture Limited, Heriot Bay, British Columbia, Canada.
authors.forename: John W
authors.initials: JW
authors.lastname: Heath
authors.affiliation: Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada Faculty of Land and Food Systems, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Anthony P
authors.initials: AP
authors.lastname: Farrell
authors.affiliation: Department of Biology, University of Western Ontario, London, Ontario, Canada bneff@uwo.ca.
authors.forename: Bryan D
authors.initials: BD
authors.lastname: Neff
mesh_terms: D000064:Acclimatization / Q000235:genetics; D000222:Adaptation, Physiological / Q000235:genetics*; D000704:Analysis of Variance; D000818:Animals; D001835:Body Weight; D001955:British Columbia; D005260:Female; D014644:Genetic Variation; D006339:Heart Rate / Q000235:genetics; D008297:Male; D010063:Ovum / Q000502:physiology; D010100:Oxygen; D012474:Salmon / Q000235:genetics / Q000502:physiology*; D013696:Temperature
chemical_list: D010100:Oxygen
keywords: aerobic capacity; climate change; egg size; evolutionary potential; heart rate; maternal effects