Genetic homogeneity in the face of morphological heterogeneity in the harbor porpoise from the Black Sea and adjacent waters (Phocoena phocoena relicta),Heredity

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Genetic homogeneity in the face of morphological heterogeneity in the harbor porpoise from the Black Sea and adjacent waters (Phocoena phocoena relicta)
Heredity ( IF 3.1 ) Pub Date : 2019-11-26 , DOI: 10.1038/s41437-019-0284-1
Yacine Ben Chehida ₁ , Julie Thumloup ₁ , Karina Vishnyakova ₂ , Pavel Gol'din ₃ , Michael C Fontaine _{1,

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Affiliation

Absence of genetic differentiation is usually taken as an evidence of panmixia, but can also reflect other situations, including even nearly complete demographic independence among large-sized populations. Deciphering which situation applies has major practical implications (e.g., in conservation biology). The endangered harbor porpoises in the Black Sea illustrates this point well. While morphological heterogeneity suggested that population differentiation may exist between individuals from the Black and Azov seas, no genetic study provided conclusive evidence or covered the entire subspecies range. Here, we assessed the genetic structure at ten microsatellite loci and a 3904 base-pairs mitochondrial fragment in 144 porpoises across the subspecies range (i.e., Aegean, Marmara, Black, and Azov seas). Analyses of the genetic structure, including FST, Bayesian clustering, and multivariate analyses revealed a nearly complete genetic homogeneity. Power analyses rejected the possibility of underpowered analyses (power to detect FST ≥ 0.008 at microsatellite loci). Simulations under various demographic models, evaluating the evolution of FST, showed that a time-lag effect between demographic and genetic subdivision is also unlikely. With a realistic effective population size of 1000 individuals, the expected “gray zone” would be at most 20 generations under moderate levels of gene flow (≤10 migrants per generation). After excluding alternative hypotheses, panmixia remains the most likely hypothesis explaining the genetic homogeneity in the Black Sea porpoises. Morphological heterogeneity may thus reflect other processes than population subdivision (e.g., plasticity, selection). This study illustrates how combining empirical and theoretical approaches can contribute to understanding patterns of weak population structure in highly mobile marine species.

中文翻译：

黑海及邻近水域港湾鼠海豚 (Phocoena phocoena relicta) 面对形态异质性的遗传同质性

缺乏遗传分化通常被视为泛混合症的证据，但也可以反映其他情况，包括大型人群中几乎完全的人口独立性。破译哪种情况适用具有重大的实际意义（例如，在保护生物学中）。黑海濒临灭绝的港湾鼠海豚很好地说明了这一点。虽然形态异质性表明来自黑海和亚速海的个体之间可能存在种群分化，但没有遗传研究提供确凿的证据或涵盖整个亚种范围。在这里，我们评估了亚种范围（即爱琴海、马尔马拉海、黑海和亚速海）144 只鼠海豚的 10 个微卫星位点和 3904 个碱基对线粒体片段的遗传结构。遗传结构分析，包括 FST、贝叶斯聚类和多变量分析，揭示了几乎完全的遗传同质性。功效分析排除了分析功效不足的可能性（在微卫星位点检测 FST ≥ 0.008 的功效）。在各种人口统计模型下进行的模拟，评估了 FST 的演变，表明人口统计和遗传细分之间也不太可能出现时滞效应。实际有效种群规模为 1000 人，在中等水平的基因流动（每代≤ 10 名移民）下，预期的“灰色地带”最多为 20 代。在排除其他假设后，panmixia 仍然是解释黑海鼠海豚遗传同质性的最可能的假设。因此，形态异质性可能反映了群体细分以外的其他过程（例如，可塑性、选择）。这项研究说明了如何结合经验和理论方法有助于理解高度流动海洋物种的弱种群结构模式。

更新日期：2019-11-26

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