Cotto Olivier, Ronce Ophélie
Université Montpellier 2, CNRS, Institut des Sciences de l'Evolution, CC65, Place Eugène Bataillon, 34095 Montpellier cedex 5, France.
Evolution. 2014 Sep;68(9):2481-93. doi: 10.1111/evo.12462. Epub 2014 Jul 9.
In this study, we use a quantitative genetics model of structured populations to investigate the evolution of senescence in a variable environment. Adaptation to local environments depends on phenotypic traits whose optimal values vary with age and with environmental conditions. We study different scenarios of environmental heterogeneity, where the environment changes abruptly, gradually, or cyclically with time and where the environment is heterogeneous in space with different populations connected by migration. The strength of selection decreases with age, which predicts slower adaptation of traits expressed late in the life cycle, potentially generating stronger senescence in habitats where selection changes in space or in time. This prediction is however complicated by the fact that the genetic variance also increases with age. Using numerical calculations, we found that the rate of senescence is generally increased when the environment varies. In particular, migration between different habitats is a source of senescence in heterogeneous landscapes. We also show that the rate of senescence can vary transiently when the population is not at equilibrium, with possible implications for experimental evolution and the study of invasive species. Our results highlight the need to study age-specific adaptation, as a changing environment can have a different impact on different age classes.
在本研究中，我们使用结构化种群的定量遗传学模型来研究可变环境中衰老的进化。对当地环境的适应取决于表型性状，其最优值随年龄和环境条件而变化。我们研究了环境异质性的不同情形，即环境随时间突然、逐渐或周期性变化，以及环境在空间上异质且不同种群通过迁移相连的情况。选择强度随年龄降低，这预示着生命周期后期表达的性状适应较慢，可能在选择在空间或时间上发生变化的栖息地产生更强的衰老。然而，这一预测因遗传方差也随年龄增加这一事实而变得复杂。通过数值计算，我们发现当环境变化时，衰老速率通常会增加。特别是，不同栖息地之间的迁移是异质景观中衰老的一个来源。我们还表明，当种群未达到平衡时，衰老速率可能会短暂变化，这可能对实验进化和入侵物种研究产生影响。我们的结果强调了研究特定年龄适应的必要性，因为变化的环境可能对不同年龄组产生不同的影响。
