Phenotypic variability can promote the evolution of adaptive plasticity by reducing the stringency of natural selection

Adaptive phenotypic plasticity is a potent but not ubiquitous solution to environmental heterogeneity, driving interest in what factors promote and limit its evolution. Here a novel computational model representing stochastic information flow in development is used to explore evolution from a constitutive phenotype to an adaptively plastic response. Results show that populations tend to evolve robustness to developmental stochasticity, but this evolved robustness limits evolvability; specifically, robust genotypes have less ability to evolve adaptive plasticity when presented with a mix of both the ancestral environment and a new environment. Analytic calculations and computational experiments confirm that this constraint occurs when the initial mutational steps toward plasticity are pleiotropic, such that mutant fitnesses decline in the environment to which their parents are well-adapted. Greater phenotypic variability improves evolvability in the model by lessening this decline as wel...适应性表型可塑性（Adaptive phenotypic plasticity）是应对环境异质性的有效但并非普适的策略，这引发了学界对促进与限制其演化的各类因素的研究兴趣。本研究采用一种表征发育过程中随机信息流的新型计算模型，探究了从组成型表型（constitutive phenotype）到适应性表型可塑性响应的演化历程。研究结果显示，种群往往会演化出对发育随机性的鲁棒性（robustness），但这种演化获得的鲁棒性会限制其演化潜能（evolvability）；具体而言，当种群同时面临祖先环境与新环境的混合条件时，具有鲁棒性的基因型演化出适应性表型可塑性的能力更弱。解析计算与计算实验证实，当指向可塑性的初始突变步骤具有多效性（pleiotropic）时，便会出现这一演化约束：此时突变体在其亲本已充分适应的环境中的适合度（fitness）会出现下降。在该模型中，更高的表型变异度可通过缓解这一下降趋势，提升种群的演化潜能……