Wild, asexual, vertebrate hybrids have many characteristics that make them good model systems for studying how genomes evolve and epigenetic modifications influence animal physiology. In particular, the formation of asexual hybrid lineages is a form of reproductive incompatibility, but we know little about the genetic and genomic mechanisms by which this mode of reproductive isolation proceeds in animals. Asexual lineages also provide researchers with the ability to produce genetically identical individuals, enabling the study of autonomous epigenetic modifications without the confounds of genetic variation. Here, we briefly review the cellular and molecular mechanisms leading to asexual reproduction in vertebrates and the known genetic and epigenetic consequences of the loss of sex. We then specifically discuss what is known about asexual lineages of Fundulus diaphanus x F. heteroclitus to highlight gaps in our knowledge of the biology of these clones. Our preliminary studies of F. diaphanus and F. heteroclitus karyotypes from Porter's Lake (Nova Scotia, Canada) agree with data from other populations, suggesting a conserved interspecific chromosomal arrangement. In addition, genetic analyses suggest that: (a) the same major clonal lineage (Clone A) of F. diaphanus x F. heteroclitus has remained dominant over the past decade, (b) some minor clones have also persisted, (c) new clones may have recently formed, and iv) wild clones still mainly descend from F. diaphanus ♀ x F. heteroclitus ♂ crosses (96% in 2017–2018). These data suggest that clone formation may be a relatively rare, but continuous process, and there are persistent environmental or genetic factors causing a bias in cross direction. We end by describing our current research on the genomic causes and consequences of a transition to asexuality and the potential physiological consequences of epigenetic variation.

中文翻译：

---

使用无性脊椎动物研究基因组进化和动物生理学：带状（Fundulus diaphanus）x普通鳉鱼（F.heteroclitus）杂交谱系作为模型系统。

野生、无性、脊椎动物杂交具有许多特征，使它们成为研究基因组进化和表观遗传修饰如何影响动物生理学的良好模型系统。特别是，无性杂交谱系的形成是生殖不相容的一种形式，但我们对这种生殖隔离模式在动物中进行的遗传和基因组机制知之甚少。无性谱系还为研究人员提供了产生基因相同个体的能力，从而能够研究自主表观遗传修饰，而不会受到遗传变异的影响。在这里，我们简要回顾了导致脊椎动物无性繁殖的细胞和分子机制，以及性丧失的已知遗传和表观遗传后果。然后，我们具体讨论了关于Fundulus diaphanus x F. 异斜线无性谱系的已知信息，以强调我们对这些克隆的生物学知识的空白。我们对波特湖（加拿大新斯科舍省）的F. diaphanus和F. 异斜线虫核型的初步研究与其他种群的数据一致，表明存在保守的种间染色体排列。此外，遗传分析表明：(a) F. diaphanus x F. 异斜线虫的相同主要克隆谱系（克隆 A）在过去十年中仍然占主导地位，(b) 一些次要克隆也持续存在，(c) 新的克隆可能是最近形成的，并且 iv) 野生克隆仍然主要来自F. diaphanus ♀ x  F. heeroclitu s ♂杂交（2017-2018 年为 96%）。这些数据表明克隆形成可能是一个相对罕见但连续的过程，并且存在持续的环境或遗传因素导致交叉方向的偏差。最后，我们描述了我们目前对无性转变的基因组原因和后果以及表观遗传变异的潜在生理后果的研究。