Whole‐genome duplication (WGD), contributing to evolutionary diversity and environmental adaptability, has been observed across a wide variety of eukaryotic groups, but not in molluscs. Molluscs are the second largest animal phylum in terms of species numbers, and among the organisms that have successfully adapted to the nonmarine realm through aquatic–terrestrial (A‐T) transition. We assembled a chromosome‐level reference genome for Achatina immaculata, a globally invasive species, and compared the genomes of two giant African snails (A. immaculata and Achatina fulica) to other available mollusc genomes. Macrosynteny, colinearity blocks, Ks peak and Hox gene clusters collectively suggested a WGD event in the two snails. The estimated WGD timing (~70 million years ago) was close to the speciation age of the Sigmurethra–Orthurethra (within Stylommatophora) lineage and the Cretaceous–Tertiary (K‐T) mass extinction, indicating that the WGD may have been a common event shared by all Sigmurethra–Orthurethra species and conferred ecological adaptability allowing survival after the K‐T extinction event. Furthermore, the adaptive mechanism of WGD in terrestrial ecosystems was confirmed by the presence of gene families related to the respiration, aestivation and immune defence. Several mucus‐related gene families expanded early in the Stylommatophora lineage, and the haemocyanin and phosphoenolpyruvate carboxykinase families doubled during WGD, and zinc metalloproteinase genes were highly tandemly duplicated after WGD. This evidence suggests that although WGD may not have been the direct driver of the A‐T transition, it played an important part in the terrestrial adaptation of giant African snails.

中文翻译：

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巨型非洲蜗牛基因组提供了对软体动物全基因组复制和水陆过渡的见解

全基因组重复 (WGD) 有助于进化多样性和环境适应性，已在各种真核生物群中观察到，但在软体动物中未观察到。就物种数量而言，软体动物是第二大动物门，并且是通过水陆 (A-T) 过渡成功适应非海洋领域的生物之一。我们为全球入侵物种Achatina immaculata组装了染色体水平的参考基因组，并比较了两种非洲巨型蜗牛（A. immaculata和Achatina fulica) 到其他可用的软体动物基因组。宏同线性、共线性块、Ks 峰和 Hox 基因簇共同表明两只蜗牛中发生了 WGD 事件。估计的 WGD 时间（约 7000 万年前）接近 Sigmurethra-Orthurethra（在茎杆目内）谱系和白垩纪-第三纪 (K-T) 大灭绝的物种形成年龄，表明 WGD 可能是一个常见事件所有 Sigmurethra-Orthurethra 物种共有，并赋予生态适应性，允许在 K-T 灭绝事件后生存。此外，与呼吸、夏眠和免疫防御相关的基因家族的存在证实了 WGD 在陆地生态系统中的适应机制。几个粘液相关基因家族在茎线虫谱系的早期扩展，WGD 期间血蓝蛋白和磷酸烯醇式丙酮酸羧激酶家族增加了一倍，WGD 后锌金属蛋白酶基因高度串联复制。这一证据表明，虽然 WGD 可能不是 A-T 过渡的直接驱动因素，但它在非洲巨型蜗牛的陆地适应中发挥了重要作用。