Hybridization masks speciation in the evolutionary history of the Galápagos marine iguana

The effects of the direct interaction between hybridization and speciation—two major contrasting evolutionary processes—are poorly understood. We present here the evolutionary history of the Galápagos marine iguana (Amblyrhynchus cristatus) and reveal a case of incipient within-island speciation, which is paralleled by between-island hybridization. In-depth genome-wide analyses suggest that Amblyrhynchus diverged from its sister group, the Galápagos land iguanas, around 4.5 million years ago (Ma), but divergence among extant populations is exceedingly young (less than 50 000 years). Despite Amblyrhynchus appearing as a single long-branch species phylogenetically, we find strong population structure between islands, and one case of incipient speciation of sister lineages within the same island—ostensibly initiated by volcanic events. Hybridization between both lineages is exceedingly rare, yet frequent hybridization with migrants from nearby islands is evident. The contemporary snapshot ...杂交与物种形成这两大相互对立的核心演化过程之间的直接交互效应，迄今仍未得到充分阐释。本文报道加拉帕戈斯海鬣蜥（Amblyrhynchus cristatus）的演化历史，并揭示了一类与岛屿间杂交现象并行存在的岛屿内部初期物种形成案例。深度全基因组分析表明，海鬣蜥与其姊妹群加拉帕戈斯陆鬣蜥的分化时间约为450万年前（Ma），但现存种群间的分化时间极短（不足5万年）。尽管从系统发育视角来看，海鬣蜥属于单系且具长分支的物种，我们仍发现不同岛屿间存在显著的种群结构，且同一岛屿内存在姊妹谱系的初期物种形成事件——该事件表面上由火山活动所触发。两类谱系之间的杂交事件极为罕见，但与来自邻近岛屿的迁徙个体间的杂交却频繁发生。本研究获取的当代种群快照……