Populations may counteract lasting temperature changes or recurrent extremes through plasticity or adaptation. However, it remains underexplored how outbreeding, either naturally, unintentionally, or facilitated, may modify a local response potential and whether genotype-by-environment interactions or between-trait correlations can restrict this potential. We quantified population differences and outbreeding effects, within-population genetic variation, and plasticity of these, for thermal performance proxy traits using 32 pedigreed wild, domesticated, and wild-domesticated Atlantic salmon families reared under common-garden conditions. Following exposure to ambient cold (11.6 °C) or ~4° and ~8° warmer summer temperatures, populations differed notably for body length and critical thermal maximum (CT_max) and for thermal plasticity of length, condition, and CT_max, but not for haematocrit. Line-cross analysis suggested mostly additive and some dominant outbreeding effects on means and solely additive outbreeding effects on plasticity. Heritability was detected for all traits. However, with increasing acclimation temperature, differences in CT_max between populations and CT_max heritability diminished, and CT_max breeding values re-ranked. Furthermore, CT_max and body size were negatively correlated at the genetic and phenotypic levels, and there was indirect evidence for a positive correlation between growth potential and thermal performance breadth for growth. Thus, population differences (including those between wild and domesticated populations) in thermal performance and plasticity may present a genetic resource in addition to the within-population genetic variance to facilitate, or impede, thermal adaptation. However, unfavourable genotype-by-environment interactions and negative between-trait correlations may generally hamper joint evolution in response to an increase in average temperature and temporary extremes.

种群可以通过可塑性或适应来抵消持久的温度变化或反复出现的极端情况。然而，自然、无意或促进的近亲繁殖如何改变局部反应潜力以及基因型与环境的相互作用或性状之间的相关性是否会限制这种潜力，仍然没有得到充分探索。我们使用在普通花园条件下饲养的 32 个纯种野生、驯化和野生驯化大西洋鲑科，量化了种群差异和远交效应、种群内遗传变异和这些的可塑性，以获得热性能代理性状。在暴露于环境寒冷 (11.6 °C) 或约 4° 和约 8° 的夏季高温后，种群的体长和临界热最大值 (CT _max) 以及长度、条件和 CT _max的热可塑性，但不适用于血细胞比容。线交叉分析表明，主要是加性和一些显性的近亲繁殖对均值的影响，而单独的加性近亲繁殖对可塑性的影响。检测到所有性状的遗传力。然而，随着驯化温度的升高，种群间CT max 和CT _max遗传力的差异减小，CT _max育种值重新排序。此外，CT_最大值和体型在遗传和表型水平上呈负相关，并且有间接证据表明生长潜力和生长的热性能广度之间呈正相关。因此，热性能和可塑性方面的种群差异（包括野生种群和驯化种群之间的差异）可能是一种遗传资源，除了种群内遗传变异外，还可以促进或阻碍热适应。然而，不利的基因型与环境的相互作用和性状之间的负相关性通常会阻碍联合进化，以应对平均温度的升高和暂时的极端情况。