An extremely high incidence of hybridization among sea turtles is found along the Brazilian coast. To understand this atypical phenomenon and its impact on sea turtle conservation, research focused in the evolutionary history of sea turtles is fundamental. We assessed high quality multilocus haplotypes of 143 samples of the five species of sea turtles that occur along the Brazilian coast to investigate the hybridization process and the population structure of hawksbill (Eretmochelys imbricata) and loggerhead turtles (Caretta caretta). The multilocus data were initially used to characterize interspecific hybrids. Introgression (F2 hybrids) was only confirmed in hatchlings of F1 hybrid females (hawksbill x loggerhead), indicating that introgression was either previously overestimated and F2 hybrids may not survive to adulthood, or the first-generation hybrid females nesting in Brazil were born as recent as few decades ago. Phylogenetic analyses using nuclear markers recovered the mtDNA-based Indo-Pacific and Atlantic lineages for hawksbill turtles, demonstrating a deep genetic divergence dating from the early Pliocene. In addition, loggerhead turtles that share a common feeding area and belong to distinct Indo-Pacific and Atlantic mtDNA clades present no clear genetic differentiation at the nuclear level. Finally, our results indicate that hawksbill and loggerhead rookeries along the Brazilian coast are likely connected by male-mediated gene flow.

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关于巴西玳瑁和红海龟杂交和种群结构的新遗传见解

沿巴西海岸发现海龟杂交的发生率极高。要了解这种非典型现象及其对海龟保护的影响，以海龟进化史为重点的研究是基础。我们评估了发生在巴西海岸的五种海龟的 143 个样本的高质量多位点单倍型，以研究玳瑁 (Eretmochelys imbricata) 和红海龟 (Caretta caretta) 的杂交过程和种群结构。多位点数据最初用于表征种间杂种。基因渗入（F2 杂种）仅在 F1 杂种雌性（玳瑁 x 蠵螈）的幼体中得到证实，表明基因渗入要么以前被高估，而 F2 杂种可能无法存活到成年，或者在巴西筑巢的第一代杂交雌性最近才出生在几十年前。使用核标记进行的系统发育分析恢复了玳瑁海龟的基于 mtDNA 的印度-太平洋和大西洋谱系，证明了上新世早期的深层遗传差异。此外，共享一个共同觅食区并属于不同的印度洋-太平洋和大西洋 mtDNA 进化枝的红海龟在核水平上没有明显的遗传分化。最后，我们的结果表明，巴西海岸的玳瑁和红蠵群可能通过雄性介导的基因流相连。证明了上新世早期的深度遗传差异。此外，共享一个共同觅食区并属于不同的印度洋-太平洋和大西洋 mtDNA 进化枝的红海龟在核水平上没有明显的遗传分化。最后，我们的结果表明，巴西海岸的玳瑁和红蠵群可能通过雄性介导的基因流相连。证明了上新世早期的深度遗传差异。此外，共享一个共同觅食区并属于不同的印度洋-太平洋和大西洋 mtDNA 进化枝的红海龟在核水平上没有明显的遗传分化。最后，我们的结果表明，巴西海岸的玳瑁和红蠵群可能通过雄性介导的基因流相连。