Genetic variation for upper thermal tolerance diminishes within and between populations with increasing acclimation temperature in Atlantic salmon

Abstract

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-byenvironment interactions and negative between-trait correlations may generally hamper joint evolution in response to an increase in average temperature and temporary extremes.

Genetic architecture of acute hyperthermia resistance in juvenile rainbow trout (Oncorhynchus mykiss) and genetic correlations with production traits

“…This difference in result between the present study and the one from Perry et al [13] might be due to genetic or environmental differences between the studied populations as was observed in Kause et al for body weight [72], the different phenotyping ages or the method to produce the families by separated or mixed family rearing. However, our result is consistent with Debes et al [64] which found in first-year Atlantic salmon a clearly negative genetic correlation of −0.86 ± 0.49 between acute hyperthermia resistance and fork length, fork length being highly correlated with body weight in Atlantic salmon [73] as well as in rainbow trout as shown in Table 3 and in Haffray et al [32]. Trade-offs were suggested between body weight and acute hyperthermia resistance in rainbow trout [11,16,24] and in fish in general [71, 74], suggesting that there are physiological mechanisms underlying this negative relationship and thus potentially genetic basis.…”

“…The discovery of a significant maternal effect at age as late as 280 dpf was surprising as generally the magnitude of the maternal effect tends towards zero within the first year of life in fish for traits like growth or survival [61, 62]. It seems that the magnitude of maternal effects on acute hyperthermia resistance also shrinks with age in salmonids: maternal effects were found to explain 77% of acute hyperthermia resistance phenotypic variance in chinook salmon Oncorhynchus tshawytscha larvae weighing between 0.6 and 3.6 g [63] while it was not significant for acute hyperthermia resistance in Atlantic salmon at 297 dpf [64].…”

Genomic dynamics of brown trout populations released to a novel environment

“…Some life history traits, for example, migratory and reproductive behavior, are influenced by intrinsic traits, for example, metabolism (Eldøy et al, 2021). These behaviors are, in turn, affected by environmental factors that may vary within populations over time and are governed by complex genetic architectures (Debes et al, 2021; Näslund et al, 2018). Further study on the dynamics of phenotypes and underlying genes is warranted.…”

Estimates of Effective Population Size in Commercial and Hatchery Strains of Coho Salmon (Oncorhynchus kisutch (Walbaum, 1792))

“…The small effective population sizes observed here are relevant to understanding future scenarios in aquaculture. For example, the ability to adapt to climate change can impact the future viability of aquaculture and natural populations [ 39 , 40 , 41 ]. The likelihood for adaptation of salmonids can be explained by long- and short-term exposure to increased water temperature.…”