Because speciation might have been promoted by ancient introgression from an extinct lineage, it is important to detect the existence of 'ghost introgression' in focal taxa and examine its contribution to their diversification. In this study, we examined possible ghost introgression and its contributions to the diversification of ricefishes of the genus Adrianichthys in Lake Poso, an ancient lake on Sulawesi Island, in which some extinctions are known to have occurred. Population-genomic analysis revealed that two extant Adrianichthys species, A. oophorus and A. poptae are reproductively isolated from each other. Comparisons of demographic models demonstrated that introgression from a ghost population, which diverged from the common ancestor of A. oophorus and A. poptae, is essential for reconstructing the demographic history of Adrianichthys. The best model estimated that the divergence of the ghost population greatly predated the divergence between A. oophorus and A. poptae, and that the ghost population secondarily contacted the two extant species within Lake Poso more recently. Genome scans and simulations detected a greatly divergent locus, which cannot be explained without ghost introgression. This locus was also completely segregated between A. oophorus and A. poptae. These findings suggest that variants that came from a ghost population have contributed to the divergence between A. oophorus and A. poptae, but the large time-lag between their divergence and ghost introgression indicates that the contribution of introgression may be restricted.

中文翻译：

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古华莱士湖中阿德里安鱼属稻鱼的幽灵渗入。

由于物种形成可能是由已灭绝谱系的古代基因渗入所促进的，因此检测焦点类群中“幽灵基因渗入”的存在并检查其对其多样化的贡献非常重要。在这项研究中，我们研究了可能的鬼渗入及其对波索湖中阿德里安鱼属稻鱼多样化的贡献，波索湖是苏拉威西岛的一个古老湖泊，已知该湖曾发生过一些灭绝事件。群体基因组分析表明，两种现存的阿德里安鱼物种，A. oophorus 和 A. poptae 彼此生殖隔离。人口统计模型的比较表明，来自幽灵种群的基因渗入对于重建阿德里安鱼的人口统计历史至关重要，该幽灵种群与 A. oophorus 和 A. poptae 的共同祖先不同。最佳模型估计，幽灵种群的分化大大早于 A. oophorus 和 A. poptae 之间的分歧，并且幽灵种群最近才接触到波索湖内的两个现存物种。基因组扫描和模拟检测到一个截然不同的基因座，如果没有幽灵基因渗入就无法解释这一点。该基因座在 A. oophorus 和 A. poptae 之间也完全分离。这些发现表明，来自幽灵种群的变体促成了 A. oophorus 和 A. poptae 之间的分化，但它们的分歧和幽灵基因渗入之间的巨大时间滞后表明基因渗入的贡献可能受到限制。