Abstract Population bottlenecks can result in loss of genetic variation, increased extinction risk, and hybridization with related sympatric species. Many challenges are associated with empirical detection of population declines, thus conservation biologists often use molecular approaches as surrogates. This study explored whether declines in abundances of viviparous sea snakes on Australia's Timor Sea reefs could have been foreshadowed using genetic surveys. Ashmore Reef (the largest Timor Sea reef) once hosted large breeding populations of sea snakes. Abundances have declined precipitously since 1994 and Ashmore Reef has been devoid of snakes since 2012. Moreover, high rates of hybridization between two sympatric species have been documented on Timor Sea reefs, possibly associated with sea snake declines. I analysed mitochondrial DNA and 11 nuclear microsatellites for >250 sea snakes from three species, Aipysurus laevis, Aipysurus fuscus and Emdocephalus annulatus, sampled on four Timor Sea reefs in 2002 and 2010. While there was strong spatial genetic structure among reefs, there was little temporal genetic divergence for A. laevis at Ashmore Reef, despite the massive declines in abundance during that temporal window. Positive Tajima's D and Fu's FS values at Ashmore Reef indicated demographic contraction for: A. laevis in 2002 and 2010; E. annulatus (2002); but not A. fuscus (2002). Microsatellites showed inbreeding depression (positive Fis values) and non-random mating (heterozygote deficit) for all three species at Ashmore Reef, consistent with population declines. Bottleneck tests were equivocal, with significant heterozygous excesses at Ashmore Reef, but non-significant M-ratios or mode-shifts in allele frequencies, with the significance of tests differing markedly with microsatellite mutation models. Thus genetic analyses alone would not have been sufficient to provide managers with unequivocal evidence of population declines. There was little evidence for hybridization between A. laevis and A. fuscus, despite previous research suggesting that the Endangered A. fuscus was at risk of reverse speciation secondary to the highly porous reproductive barriers between these species.

中文翻译：

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澳大利亚帝汶海珊瑚礁上海蛇的种群数量下降、遗传瓶颈和潜在杂交

摘要 种群瓶颈会导致遗传变异的丧失、灭绝风险的增加以及与相关同域物种的杂交。许多挑战与人口下降的经验检测有关，因此保护生物学家经常使用分子方法作为替代方法。这项研究探讨了澳大利亚帝汶海珊瑚礁上胎生海蛇丰度的下降是否可以通过基因调查来预测。Ashmore Reef（帝汶海最大的珊瑚礁）曾经是海蛇的大量繁殖地。自 1994 年以来，数量急剧下降，而阿什莫尔礁自 2012 年以来就没有蛇。此外，在帝汶海珊瑚礁上记录了两种同域物种之间的高杂交率，这可能与海蛇减​​少有关。我分析了 2002 年和 2010 年在四个帝汶海珊瑚礁上采样的来自三个物种（Aipysurus laevis、Aipysurus fuscus 和 Emdocephalus annulatus）的线粒体 DNA 和 11 个核微卫星的线粒体 DNA 和 11 颗核微卫星。虽然珊瑚礁之间有很强的空间遗传结构，但几乎没有尽管在该时间窗口期间丰度大幅下降，但 Ashmore Reef 的 A. laevis 的时间遗传差异。Ashmore Reef Tajima 的 D 和 Fu 的 FS 值为正值表明以下种群的人口收缩： 2002 年和 2010 年的 A. laevis；E. annulatus (2002); 但不是 A. fuscus (2002)。微卫星在 Ashmore Reef 的所有三个物种都显示近交抑制（正 Fis 值）和非随机交配（杂合子缺陷），这与种群下降一致。瓶颈测试是模棱两可的，Ashmore Reef 存在显着的杂合过量，但等位基因频率的 M 比或模式转移不显着，测试的意义与微卫星突变模型显着不同。因此，仅靠遗传分析不足以为管理者提供种群下降的明确证据。尽管先前的研究表明濒临灭绝的 A. fuscus 由于这些物种之间高度多孔的生殖屏障而处于反向物种形成的风险中，但几乎没有证据表明 A. laevis 和 A. fuscus 之间存在杂交。因此，仅靠遗传分析不足以为管理者提供种群下降的明确证据。尽管先前的研究表明濒临灭绝的 A. fuscus 由于这些物种之间高度多孔的生殖屏障而处于反向物种形成的风险中，但几乎没有证据表明 A. laevis 和 A. fuscus 之间存在杂交。因此，仅靠遗传分析不足以为管理者提供种群下降的明确证据。尽管先前的研究表明濒临灭绝的 A. fuscus 由于这些物种之间高度多孔的生殖屏障而处于反向物种形成的风险中，但几乎没有证据表明 A. laevis 和 A. fuscus 之间存在杂交。