Cressler Clayton E, Bengtson Stefan, Nelson William A
Am Nat. 2017 Jul;190(1):E13-E27. doi: 10.1086/691779. Epub 2017 Apr 6.
Individual differences in genetics, age, or environment can cause tremendous differences in individual life-history traits. This individual heterogeneity generates demographic heterogeneity at the population level, which is predicted to have a strong impact on both ecological and evolutionary dynamics. However, we know surprisingly little about the sources of individual heterogeneity for particular taxa or how different sources scale up to impact ecological and evolutionary dynamics. Here we experimentally study the individual heterogeneity that emerges from both genetic and nongenetic sources in a species of freshwater zooplankton across a large gradient of food quality. Despite the tight control of environment, we still find that the variation from nongenetic sources is greater than that from genetic sources over a wide range of food quality and that this variation has strong positive covariance between growth and reproduction. We evaluate the general consequences of genetic and nongenetic covariance for ecological and evolutionary dynamics theoretically and find that increasing nongenetic variation slows evolution independent of the correlation in heritable life-history traits but that the impact on ecological dynamics depends on both nongenetic and genetic covariance. Our results demonstrate that variation in the relative magnitude of nongenetic versus genetic sources of variation impacts the predicted ecological and evolutionary dynamics.
遗传学、年龄或环境方面的个体差异会导致个体生活史特征产生巨大差异。这种个体异质性在种群水平上产生了种群统计学异质性，预计这会对生态和进化动态产生强烈影响。然而，令人惊讶的是，我们对特定分类群的个体异质性来源，或者不同来源如何累积影响生态和进化动态知之甚少。在此，我们通过实验研究了一种淡水浮游动物在食物质量的大梯度范围内，由遗传和非遗传来源产生的个体异质性。尽管对环境进行了严格控制，但我们仍然发现，在广泛的食物质量范围内，非遗传来源的变异大于遗传来源的变异，并且这种变异在生长和繁殖之间具有很强的正协方差。我们从理论上评估了遗传和非遗传协方差对生态和进化动态的总体影响，发现增加非遗传变异会减缓进化，而与可遗传生活史特征的相关性无关，但对生态动态的影响则取决于非遗传和遗传协方差。我们的结果表明，非遗传变异与遗传变异来源的相对大小差异会影响预测的生态和进化动态。
