Schneider Ralf F, Meyer Axel
Lehrstuhl für Zoologie und Evolutionsbiologie, Department of Biology, University of Konstanz, Universitaetstrasse 10, 78457, Konstanz, Germany.
Mol Ecol. 2017 Jan;26(1):330-350. doi: 10.1111/mec.13880. Epub 2016 Nov 14.
There is increasing evidence that phenotypic plasticity can promote population divergence by facilitating phenotypic diversification and, eventually, genetic divergence. When a 'plastic' population colonizes a new habitat, it has the possibility to occupy multiple niches by expressing several distinct phenotypes. These initially reflect the population's plastic range but may later become genetically fixed by selection via the process of 'genetic assimilation' (GA). Through this process multiple specialized sister lineages can arise that share a common plastic ancestor - the 'flexible stem'. Here, we review possible molecular mechanisms through which natural selection could fix an initially plastic trait during GA. These mechanisms could also explain how GA may contribute to cryptic genetic variation that can subsequently be coopted into other phenotypes or traits, but also lead to nonadaptive responses. We outline the predicted patterns of genetic and transcriptional divergence accompanying flexible stem radiations. The analysis of such patterns of (retained) adaptive and nonadaptive plastic responses within and across radiating lineages can inform on the state of ongoing GA. We conclude that, depending on the stability of the environment, the molecular architecture underlying plastic traits can facilitate diversification, followed by fixation and consolidation of an adaptive phenotype and degeneration of nonadaptive ones. Additionally, the process of GA may increase the cryptic genetic variation of populations, which on one hand may serve as substrate for evolution, but on another may be responsible for nonadaptive responses that consolidate local allopatry and thus reproductive isolation.
越来越多的证据表明，表型可塑性能够通过促进表型多样化并最终实现遗传分化，进而推动种群分化。当一个“可塑性”种群定殖到一个新栖息地时，它有可能通过表达几种不同的表型来占据多个生态位。这些表型最初反映了种群的可塑性范围，但随后可能会通过“遗传同化”（GA）过程经选择而在基因上固定下来。通过这个过程，可以产生多个共享一个共同可塑性祖先——“灵活主干”的特化姐妹谱系。在这里，我们回顾了自然选择在遗传同化过程中固定初始可塑性性状可能的分子机制。这些机制还可以解释遗传同化如何导致隐性遗传变异，这些变异随后可能被纳入其他表型或性状，但也会导致非适应性反应。我们概述了伴随灵活主干辐射的遗传和转录分化的预测模式。对辐射谱系内和辐射谱系间（保留的）适应性和非适应性可塑性反应模式的分析，可以为正在进行的遗传同化状态提供信息。我们得出结论，根据环境的稳定性，可塑性性状的分子结构可以促进多样化，随后固定和巩固适应性表型，使非适应性表型退化。此外，遗传同化过程可能会增加种群的隐性遗传变异，这一方面可能作为进化的底物，但另一方面可能导致巩固局部异域性从而导致生殖隔离的非适应性反应。
