The final formation of the Central American Isthmus (CAI) about 3.5 Ma altered global ocean circulation, connected North and South America terrestrial biotas and established the Caribbean Sea. The nature of this event creates a natural scenario to test vicariance, divergence, and speciation by allopatry. Studies have shown the effect of the CAI on marine and terrestrial species, but none have examined a large-bodied amphibious taxon. We used RAD sequencing on populations of the American crocodile (Crocodylus acutus), to study the genomic variation of C. acutus on both sides of the CAI, infer its demographic history and measure thse effect of the opening of the Panama Canal. Our results showed three genomic clusters: 1) Caribbean and the Panama Canal, 2) Pacific coast, and 3) Coiba island. The estimated divergence times between the Caribbean and Pacific populations are about 20 ka, which is younger than the formation of the CAI, coinciding with the Last Glacial Maximum. We hypothesize the glacial/interglacial cycles facilitated gene flow between the Caribbean and Pacific crocodile populations after the formation of the CAI, masking any genomic divergence the CAI may have caused. There is no evidence of gene flow associated with the opening of the Panama Canal. This article is protected by copyright. All rights reserved.

中文翻译：

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中美洲地峡对美洲鳄 (Crocodylus acutus) 基因流动和分化的影响

大约 3.5 Ma 的中美洲地峡 (CAI) 的最终形成改变了全球海洋环流，连接了北美和南美陆地生物群并建立了加勒比海。这一事件的性质创造了一个自然场景来测试变异、分歧和物种形成的异域分布。研究表明 CAI 对海洋和陆地物种的影响，但没有人研究过大型两栖类群。我们对美洲鳄 (Crocodylus acutus) 种群使用 RAD 测序，研究 CAI 两侧 C. acutus 的基因组变异，推断其人口统计历史并衡量巴拿马运河开通的影响。我们的结果显示了三个基因组簇：1) 加勒比海和巴拿马运河，2) 太平洋沿岸，以及 3) Coiba 岛。加勒比和太平洋人口之间的估计分歧时间约为 20 ka，这比 CAI 的形成更年轻，与末次盛冰期相吻合。我们假设在 CAI 形成后，冰期/间冰期循环促进了加勒比和太平洋鳄鱼种群之间的基因流动，掩盖了 CAI 可能导致的任何基因组差异。没有证据表明基因流动与巴拿马运河的开通有关。本文受版权保护。版权所有。掩盖 CAI 可能引起的任何基因组差异。没有证据表明基因流动与巴拿马运河的开通有关。本文受版权保护。版权所有。掩盖 CAI 可能引起的任何基因组差异。没有证据表明基因流动与巴拿马运河的开通有关。本文受版权保护。版权所有。