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Abstract：
Plasticity is found in all domains of life and is particularly relevant when populations experience variable environmental conditions. Traditionally, evolutionary models of plasticity are non-mechanistic: they typically view reactions norms as the target of selection, without considering the underlying genetics explicitly. Consequently, there have been difficulties in understanding the emergence of plasticity, and in explaining its limits and costs. In this paper, we offer a novel mechanistic approximation for the emergence and evolution of plasticity. We simulate random \"epigenetic mutations\" in the genotype-phenotype mapping, of the kind enabled by DNA-methylations/demethylations. The frequency of epigenetic mutations at loci affecting the phenotype is sensitive to organism stress (trait-environment mismatch), but is also genetically determined and evolvable. Thus, the \"random motion\" of epigenetic markers enables developmental learning-like behaviors that can improve adaptation within the limits imposed by the genotypes. However, with random motion being \"goal-less,\" this mechanism is also vulnerable to developmental noise leading to maladaptation. Our individual-based simulations show that epigenetic mutations can hide alleles that are temporarily unfavorable, thus enabling cryptic genetic variation. These alleles can be advantageous at later times, under regimes of environmental change, in spite of the accumulation of genetic loads. Simulations also demonstrate that plasticity is favored by natural selection in constant environments, but more under periodic environmental change. Plasticity also evolves under directional environmental change as long as the pace of change is not too fast and costs are low.
摘要：
可塑性存在于生命的所有领域，当人群经历可变的环境条件时尤其相关。传统上,可塑性的进化模型是非机械性的：他们通常将反应规范视为选择的目标，没有明确考虑潜在的遗传学。因此,很难理解可塑性的出现，并解释其局限性和成本。在本文中,我们为可塑性的出现和演化提供了一种新的机械近似。我们在基因型-表型作图中模拟随机的“表观遗传突变”，由DNA甲基化/去甲基化实现的那种。影响表型的基因座处的表观遗传突变的频率对生物体应激(性状-环境错配)敏感,但也是基因决定和进化的。因此，表观遗传标记的“随机运动”使发育学习样行为能够在基因型施加的限制内提高适应性。然而,随机运动是“无目标”，“这种机制也容易受到发育噪音的影响，导致适应不良。我们基于个体的模拟表明，表观基因突变可以隐藏暂时不利的等位基因，从而实现隐秘的遗传变异。这些等位基因在以后可能是有利的，在环境变化的制度下，尽管遗传负荷的积累。模拟还表明，可塑性在恒定环境中受到自然选择的青睐，但更多的是在周期性的环境变化下。只要变化的速度不太快且成本较低，可塑性也会在方向性环境变化下演变。
