Frequent independent origins of environmental sex determination (ESD) are assumed within amniotes. However, the phylogenetic distribution of sex‐determining modes suggests that ESD is likely very ancient and may be homologous across ESD groups. Sex chromosomes are demonstrated to be old and stable in endothermic (mammals and birds) and many ectothermic (non‐avian reptiles) lineages, but they are mostly non‐homologous between individual amniote lineages. The phylogenetic pattern may be explained by ancestral ESD with multiple transitions to later evolutionary stable genotypic sex determination. It is pointed out here that amniote ESD shares several key aspects with sequential hermaphroditism of fishes such as a lack of sex differences in genomes, biased population sex ratios, and potentially also molecular mechanism related to general stress responses. Here, it is speculated that ESD evolves via a heterochronic shift of the sensitive period of sex change from the adult to the embryonic stage in a hermaphroditic amniote ancestor. Also see the video abstract here https://youtu.be/q2mjtlCefu4.

中文翻译：

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羊膜中性别决定的演变：压力和顺序雌雄同体是否会产生环境决定？

在羊膜动物中假设环境性别决定（ESD）的频繁独立起源。然而，性别决定模式的系统发育分布表明 ESD 可能非常古老并且可能在 ESD 群体中是同源的。性染色体在吸热（哺乳动物和鸟类）和许多变温（非鸟类爬行动物）谱系中被证明是古老而稳定的，但它们在单个羊膜谱系之间大多是非同源的。系统发育模式可以通过祖先的 ESD 来解释，其中多次过渡到后来的进化稳定基因型性别决定。这里指出，羊膜 ESD 与鱼类的连续雌雄同体有几个关键方面，例如基因组中缺乏性别差异、种群性别比例有偏差、以及与一般应激反应相关的潜在分子机制。在这里，推测 ESD 是通过雌雄同体羊膜动物祖先的性别变化敏感期从成人到胚胎阶段的异时转移而进化的。另请参阅此处的视频摘要 https://youtu.be/q2mjtlCefu4。