Vogt Günter
Faculty of Biosciences, University of Heidelberg, Im Neuenheimer Feld 234, 69120 Heidelberg, Germany.
Curr Zool. 2022 Dec 2;69(4):426-441. doi: 10.1093/cz/zoac094. eCollection 2023 Aug.
Clonal organisms are particularly useful to investigate the contribution of epigenetics to phenotypic plasticity, because confounding effects of genetic variation are negligible. In the last decade, the apomictic parthenogenetic marbled crayfish, , has been developed as a model to investigate the relationships between phenotypic plasticity and genetic and epigenetic diversity in detail. This crayfish originated about 30 years ago by autotriploidy from a single slough crayfish . As the result of human releases and active spreading, marbled crayfish has established numerous populations in very diverse habitats in 22 countries from the tropics to cold temperate regions. Studies in the laboratory and field revealed considerable plasticity in coloration, spination, morphometric parameters, growth, food preference, population structure, trophic position, and niche width. Illumina and PacBio whole-genome sequencing of marbled crayfish from representatives of 19 populations in Europe and Madagascar demonstrated extremely low genetic diversity within and among populations, indicating that the observed phenotypic diversity and ability to live in strikingly different environments are not due to adaptation by selection on genetic variation. In contrast, considerable differences were found between populations in the DNA methylation patterns of hundreds of genes, suggesting that the environmentally induced phenotypic plasticity is mediated by epigenetic mechanisms and corresponding changes in gene expression. Specific DNA methylation fingerprints persisted in local populations over successive years indicating the existence of epigenetic ecotypes, but there is presently no information as to whether these epigenetic signatures are transgenerationally inherited or established anew in each generation and whether the recorded phenotypic plasticity is adaptive or nonadaptive.
克隆生物对于研究表观遗传学对表型可塑性的贡献特别有用，因为遗传变异的混杂效应可以忽略不计。在过去十年中，孤雌生殖的大理石纹螯虾已被开发为一个模型，用于详细研究表型可塑性与遗传和表观遗传多样性之间的关系。这种螯虾大约在30年前由一种单一的沼泽螯虾通过自体三倍体产生。由于人类的放生和积极扩散，大理石纹螯虾已在从热带到寒温带地区的22个国家的非常多样的栖息地中建立了众多种群。实验室和野外研究表明，大理石纹螯虾在颜色、刺、形态测量参数、生长、食物偏好、种群结构、营养级和生态位宽度方面具有相当大的可塑性。对来自欧洲和马达加斯加19个种群代表的大理石纹螯虾进行的Illumina和PacBio全基因组测序表明，种群内部和种群之间的遗传多样性极低，这表明观察到的表型多样性和生活在截然不同环境中的能力并非由于对遗传变异的选择适应。相比之下，在数百个基因的DNA甲基化模式上，不同种群之间发现了相当大的差异，这表明环境诱导的表型可塑性是由表观遗传机制和基因表达的相应变化介导的。特定的DNA甲基化指纹在当地种群中连续多年持续存在，表明存在表观遗传生态型，但目前尚无关于这些表观遗传特征是跨代遗传还是在每一代中重新建立，以及所记录的表型可塑性是适应性的还是非适应性的信息。
