Department of Biology, Washington University in Saint Louis, Box 1137, One Brookings Drive, Saint Louis, MO 63130, USA.
J Hered. 2010 Jul-Aug;101(4):391-402. doi: 10.1093/jhered/esq036. Epub 2010 Apr 7.
Reef fishes disperse primarily as oceanic "pelagic" larvae, and debate continues over the extent of this dispersal, with recent evidence for geographically restricted (closed) populations in some species. In contrast, moray eels have the longest pelagic larval stages among reef fishes, possibly providing opportunities to disperse over great distances. We test this prediction by measuring mitochondrial DNA (mtDNA) and nuclear DNA variation in 2 species of moray eels, Gymnothorax undulatus (N = 165) and G. flavimarginatus (N = 124), sampled at 14-15 locations across the Indo-Pacific. The mtDNA data comprise 632 bp of cytochrome b and 596 bp of cytochrome oxidase I. Nuclear markers include 2 recombination-activating loci (421 bp of RAG-1 and 754 bp of RAG-2). Analyses of molecular variance and Mantel tests indicate little or no genetic differentiation, and no isolation by distance, across 22 000 km of the Indo-Pacific. We estimate that mitochondrial genetic variation coalesces within the past about 2.3 million years (My) for G. flavimarginatus and within the past about 5.9 My for G. undulatus. Permutation tests of geographic distance on the mitochondrial haplotype networks indicate recent range expansions for some younger haplotypes (estimated within approximately 600 000 years) and episodic fragmentation of populations at times of low sea level. Our results support the predictions that the extended larval durations of moray eels enable ocean-wide genetic continuity of populations. This is the first phylogeographic survey of the moray eels, and morays are the first reef fishes known to be genetically homogeneous across the entire Indo-Pacific.
珊瑚礁鱼类主要作为海洋中的“浮游”幼体进行扩散，关于这种扩散的程度仍存在争议，最近有证据表明某些物种存在地理范围受限（封闭）的种群。相比之下，海鳝在珊瑚礁鱼类中具有最长的浮游幼体阶段，这可能为远距离扩散提供了机会。我们通过测量分布在印度 - 太平洋地区14 - 15个地点的2种海鳝（波纹裸胸鳝，N = 165；黄边裸胸鳝，N = 124）的线粒体DNA（mtDNA）和核DNA变异来检验这一预测。mtDNA数据包括632 bp的细胞色素b和596 bp的细胞色素氧化酶I。核标记包括2个重组激活位点（RAG - 1的421 bp和RAG - 2的754 bp）。分子方差分析和Mantel检验表明，在横跨22000公里的印度 - 太平洋区域内，几乎没有或不存在遗传分化，也没有距离隔离现象。我们估计，黄边裸胸鳝的线粒体遗传变异在过去约230万年（My）内合并，波纹裸胸鳝在过去约590万年（My）内合并。对线粒体单倍型网络进行地理距离的置换检验表明，一些较年轻的单倍型（估计在约60万年之内）近期有范围扩张，并且在海平面较低时期种群出现过偶发的片段化。我们的结果支持了这样的预测，即海鳝延长的幼体持续时间使得种群在全海洋范围内具有遗传连续性。这是首次对海鳝进行系统发育地理学调查，并且海鳝是已知在整个印度 - 太平洋地区基因同质化的首批珊瑚礁鱼类。
