Human‐mediated hybridization threatens many native species, but the effects of introgressive hybridization on life‐history expression are rarely quantified, especially in vertebrates. We quantified the effects of non‐native rainbow trout admixture on important life‐history traits including growth and partial migration behavior in three populations of westslope cutthroat trout over five years. Rainbow trout admixture was associated with increased summer growth rates in all populations and decreased spring growth rates in two populations with cooler spring temperatures. These results indicate that non‐native admixture may increase growth under warmer conditions, but cutthroat trout have higher growth rates during cooler periods. Non‐native admixture consistently increased expression of migratory behavior, suggesting that there is a genomic basis for life‐history differences between these species. Our results show that effects of interspecific hybridization on fitness traits can be the product of genotype‐by‐environment interactions even when there are minor differences in environmental optima between hybridizing species. These results also indicate that while environmentally mediated traits like growth may play a role in population‐level consequences of admixture, strong genetic influences on migratory life‐history differences between these species likely explains the continued spread of non‐native hybridization at the landscape‐level, despite selection against hybrids at the population‐level.

中文翻译：

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杂交改变了本地鳟鱼的生长和洄游生活史表达


人类介导的杂交威胁着许多本地物种，但渐渗杂交对生活史表达的影响很少被量化，特别是在脊椎动物中。我们量化了非本地虹鳟鱼混合物对重要生活史特征的影响，包括五年内三个西坡切喉鳟鱼种群的生长和部分迁徙行为。虹鳟鱼混合物与所有种群的夏季生长率增加有关，而春季温度较低的两个种群的春季生长率下降有关。这些结果表明，非本地混合物可能会在温暖的条件下促进生长，但切喉鳟鱼在寒冷的时期有更高的生长速度。非本地混合物持续增加了迁徙行为的表达，表明这些物种之间的生活史差异存在基因组基础。我们的结果表明，即使杂交物种之间的最适环境存在微小差异，种间杂交对适应性特征的影响也可能是基因型与环境相互作用的产物。这些结果还表明，虽然生长等环境介导的性状可能在混合的种群水平后果中发挥作用，但对这些物种之间迁徙生活史差异的强烈遗传影响可能解释了非本地杂交在景观水平上的持续传播，尽管在群体水平上对杂种进行了选择。