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首页> 外文期刊>Zoologica Scripta: An International Journal of Evolutionary Zoology >Linking DNA sequences to morphology: cryptic diversity and population genetic structure in the marine nematode Thoracostoma trachygaster (Nematoda, Leptosomatidae)
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Linking DNA sequences to morphology: cryptic diversity and population genetic structure in the marine nematode Thoracostoma trachygaster (Nematoda, Leptosomatidae)

机译：将DNA序列与形态联系起来：海洋线虫胸腔棘线虫（线虫，线虫科）中的隐性多样性和种群遗传结构

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摘要

Recent taxonomic and population genetic studies have revealed the presence of substantial cryptic diversity through sequence analysis of nematode morphospecies classified in different major clades. Correct interpretations of intra- and interspecific genetic variation require certainty about the conspecificity of the sequenced specimens, which in turn must depend on appropriate protocols with built-in verifiability procedures. In this study, we performed a population genetic study in the free-living marine nematode Thoracostoma trachygaster, a member of one of the earliest major clades to diverge in nematode phylogeny. We collected 367 nematodes from 11 populations located in the Californian Bight, all of which were video captured before DNA extraction to document and verify their individual morphology. Sequences for the cytochrome c oxidase subunit 1 (COI), D2D3 and 18S genes showed eight deeply divergent clades, and using a reverse taxonomy approach, six of these clades proved to be other morphospecies than T. trachygaster. Phylogenetic analyses of COI, internal transcribed spacer and D2D3 showed evidence for two sympatrically distributed cryptic species within the morphospecies T. trachygaster. Population genetic analyses of the most widespread cryptic species showed a moderate genetic structuring (Theta(ST) = 0.28), and 18% of this genetic variation was caused by differences between populations north and south of Point Conception. Within the southern Californian Bight, some genetic differentiation could be attributed to differences between populations north and south of Malibu, supporting the idea of a barrier to gene flow near Los Angeles region. The results for T. trachygaster support the contention that species diversity within free-living nematodes is underestimated, and that dispersal of marine nematodes from tidal environments associated with kelp holdfasts is substantial at scales of a few 100 km.
机译：最近的分类学和种群遗传学研究通过对分类在不同主要进化枝中的线虫形态物种进行序列分析，揭示了存在大量隐秘多样性的可能性。对种内和种间遗传变异的正确解释需要确定测序标本的同质性，而这又必须取决于具有内置可验证性程序的适当方案。在这项研究中，我们在自由活动的海洋线虫胸腔棘线虫中进行了种群遗传研究，这是最早在线虫系统发育中分化的主要进化枝之一的成员。我们从位于加利福尼亚湾的11个种群中收集了367条线虫，在提取DNA之前对所有线虫进行了视频捕获，以记录和验证其个体形态。细胞色素C氧化酶亚基1（COI），D2D3和18S基因的序列显示了8个深度不同的进化枝，并且使用反向分类法，这些进化枝中的6个被证明是中华绒螯蟹以外的其他形态物种。对COI，内部转录间隔区和D2D3进行的系统进化分析表明，形态上存在着两个特异的T. trachygaster隐性物种。对最广泛的隐性物种的种群遗传学分析显示出中等的遗传结构（Theta（ST）= 0.28），而这种遗传变异的18％是由Point Conception北部和南部种群之间的差异引起的。在南加利福尼亚州的海岸线内，某些遗传分化可能归因于马里布北部和南部种群之间的差异，这支持在洛杉矶地区附近阻碍基因流动的想法。 T. trachygaster的结果支持这样一个论点，即自由活动线虫内的物种多样性被低估了，与海藻固着物相关的潮汐环境中海洋线虫的扩散在几百公里的范围内是相当大的。

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