Price Trevor D, Qvarnström Anna, Irwin Darren E
Department of Ecology and Evolution, University of Chicago, Chicago, IL 60637, USA.
Proc Biol Sci. 2003 Jul 22;270(1523):1433-40. doi: 10.1098/rspb.2003.2372.
Models of population divergence and speciation are often based on the assumption that differences between populations are due to genetic factors, and that phenotypic change is due to natural selection. It is equally plausible that some of the differences among populations are due to phenotypic plasticity. We use the metaphor of the adaptive landscape to review the role of phenotypic plasticity in driving genetic evolution. Moderate levels of phenotypic plasticity are optimal in permitting population survival in a new environment and in bringing populations into the realm of attraction of an adaptive peak. High levels of plasticity may increase the probability of population persistence but reduce the likelihood of genetic change, because the plastic response itself places the population close to a peak. Moderate levels of plasticity arise whenever multiple traits, some of which are plastic and others not, form a composite trait involved in the adaptive response. For example, altered behaviours may drive selection on morphology and physiology. Because there is likely to be a considerable element of chance in which behaviours become established, behavioural change followed by morphological and physiological evolution may be a potent force in driving evolution in novel directions. We assess the role of phenotypic plasticity in stimulating evolution by considering two examples from birds: (i) the evolution of red and yellow plumage coloration due to carotenoid consumption; and (ii) the evolution of foraging behaviours on islands. Phenotypic plasticity is widespread in nature and may speed up, slow down, or have little effect on evolutionary change. Moderate levels of plasticity may often facilitate genetic evolution but careful analyses of individual cases are needed to ascertain whether plasticity has been essential or merely incidental to population differentiation.
种群之间的差异是由遗传因素造成的，而表型变化是由自然选择导致的。同样合理的是，种群之间的一些差异可能是由于表型可塑性。我们用适应性景观这个比喻来审视表型可塑性在推动基因进化中的作用。适度的表型可塑性在使种群在新环境中生存以及使种群进入适应性峰值的吸引域方面是最优的。高度的可塑性可能会增加种群持续存在的概率，但会降低基因变化的可能性，因为可塑性反应本身会使种群接近一个峰值。只要多个性状（其中一些是可塑的，另一些不是）形成参与适应性反应的复合性状，就会出现适度水平的可塑性。例如，行为的改变可能会推动对形态和生理的选择。由于行为的形成可能存在相当大的偶然性，行为改变随后伴随着形态和生理进化可能是推动进化朝着新方向发展的一股强大力量。我们通过考虑鸟类的两个例子来评估表型可塑性在刺激进化中的作用：（i）由于类胡萝卜素消耗导致的红色和黄色羽毛颜色的进化；（ii）岛屿上觅食行为的进化。表型可塑性在自然界中广泛存在，它可能会加速、减缓或对进化变化几乎没有影响。适度水平的可塑性通常可能会促进基因进化，但需要对个别案例进行仔细分析，以确定可塑性对于种群分化是至关重要还是仅仅是偶然的。
