Karl S A, Bowen B W, Avise J C
Department of Genetics, University of Georgia, Athens 30602.
Genetics. 1992 May;131(1):163-73. doi: 10.1093/genetics/131.1.163.
We introduce an approach for the analysis of Mendelian polymorphisms in nuclear DNA (nDNA), using restriction fragment patterns from anonymous single-copy regions amplified by the polymerase chain reaction, and apply this method to the elucidation of population structure and gene flow in the endangered green turtle, Chelonia mydas. Seven anonymous clones isolated from a total cell DNA library were sequenced to generate primers for the amplification of nDNA fragments. Nine individuals were screened for restriction site polymorphisms at these seven loci, using 40 endonucleases. Two loci were monomorphic, while the remainder exhibited a total of nine polymorphic restriction sites and three size variants (reflecting 600-base pair (bp) and 20-bp deletions and a 20-bp insertion). A total of 256 turtle specimens from 15 nesting populations worldwide were then scored for these polymorphisms. Genotypic proportions within populations were in accord with Hardy-Weinberg expectations. Strong linkage disequilibrium observed among polymorphic sites within loci enabled multisite haplotype assignments. Estimates of the standardized variance in haplotype frequency among global collections (FST = 0.17), within the Atlantic-Mediterranean (FST = 0.13), and within the Indian-Pacific (FST = 0.13), revealed a moderate degree of population substructure. Although a previous study concluded that nesting populations appear to be highly structured with respect to female (mitochondrial DNA) lineages, estimates of Nm based on nDNA data from this study indicate moderate rates of male-mediated gene flow. A positive relationship between genetic similarity and geographic proximity suggests historical connections and/or contemporary gene flow between particular rookery populations, likely via matings on overlapping feeding grounds, migration corridors or nonnatal rookeries.
我们介绍了一种分析核DNA（nDNA）中孟德尔多态性的方法，该方法利用聚合酶链反应扩增的匿名单拷贝区域的限制性片段模式，并将此方法应用于濒危绿海龟（蠵龟）种群结构和基因流动的阐明。从总细胞DNA文库中分离出7个匿名克隆并进行测序，以生成用于扩增nDNA片段的引物。使用40种核酸内切酶在这7个位点筛选了9个个体的限制性位点多态性。两个位点是单态的，其余位点共表现出9个多态性限制性位点和3个大小变异（分别反映600碱基对（bp）和20 bp的缺失以及一个20 bp的插入）。然后对来自全球15个筑巢种群的总共256个海龟标本进行这些多态性评分。种群内的基因型比例符合哈迪-温伯格预期。在基因座内的多态性位点之间观察到的强连锁不平衡使得能够进行多位点单倍型分配。全球样本中（FST = 0.17）、大西洋-地中海区域内（FST = 0.13）以及印度洋-太平洋区域内（FST = 0.13）单倍型频率的标准化方差估计显示出中等程度的种群亚结构。尽管先前的一项研究得出结论，筑巢种群在雌性（线粒体DNA）谱系方面似乎具有高度的结构，但基于本研究的nDNA数据估计的Nm表明雄性介导的基因流动速率适中。遗传相似性与地理距离之间的正相关关系表明特定繁殖群体之间存在历史联系和/或当代基因流动，可能是通过在重叠的觅食地、洄游通道或非出生地繁殖群体上的交配实现的。
