David Solomon R, Wright Jeremy J
Department of Biological Sciences, Nicholls State University, Thibodaux, Louisiana, United States of America.
New York State Museum, Albany, New York, United States of America.
J Exp Zool B Mol Dev Evol. 2017 Nov;328(7):596-606. doi: 10.1002/jez.b.22772. Epub 2017 Oct 5.
The spotted gar (Lepisosteus oculatus) shows a disjunct natural distribution, with a core population extending from the central Mississippi River Basin to the U.S. gulf coast and a peripheral population in the southern Great Lakes Basin. Despite significant conservation concerns for this species in the Great Lakes watersheds where it occurs, few genetic examinations and comparisons of these populations have been performed. We investigated inter- and intrapopulational variation in several mitochondrial genetic markers (cytochrome oxidase subunit I, COI; cytochrome oxidase subunit II, COII; and 16S rRNA, 16S) from spotted gars taken from core and peripheral populations. Genetic diversity was highest in the Mississippi River Basin and lowest in the Great Lakes Basin, while the Nueces River Basin (Texas) population showed the greatest level of divergence from other populations. Average genetic distance among core and peripheral populations was over an order of magnitude less than that seen between L. oculatus and its sister species, the Florida gar (L. platyrhincus), although a significant correlation was found between genetic and geographical distance in L. oculatus. Genetic divergence in spotted gars is likely to be related to a combination of geographic isolation and founder effects associated with recent colonization following glacial retreat. Despite its apparent lack of significant genetic differentiation or haplotype diversity, the Great Lakes population of spotted gars has previously been shown to be a unique component of the species, and additional studies are needed to determine the genetic mechanisms underlying regional adaptations as well as potential morphological differentiation among spotted gar populations.
雀鳝（Lepisosteus oculatus）呈现出间断的自然分布，其核心种群从密西西比河中游流域延伸至美国墨西哥湾沿岸，而在五大湖盆地南部有一个边缘种群。尽管在其出现的五大湖流域该物种面临重大的保护问题，但对这些种群的基因检测和比较却很少进行。我们研究了从核心种群和边缘种群采集的雀鳝的几个线粒体基因标记（细胞色素氧化酶亚基I，COI；细胞色素氧化酶亚基II，COII；以及16S核糖体RNA，16S）的种群间和种群内变异。遗传多样性在密西西比河流域最高，在五大湖流域最低，而努埃塞斯河流域（得克萨斯州）的种群与其他种群的差异程度最大。核心种群和边缘种群之间的平均遗传距离比雀鳝与其近缘物种佛罗里达雀鳝（L. platyrhincus）之间的遗传距离小一个数量级以上，尽管在雀鳝中发现遗传距离与地理距离之间存在显著相关性。雀鳝的遗传分化可能与地理隔离以及与冰川消退后近期殖民化相关的奠基者效应的综合作用有关。尽管五大湖的雀鳝种群显然缺乏显著的遗传分化或单倍型多样性，但此前已表明它是该物种的一个独特组成部分，需要进一步研究以确定区域适应性以及雀鳝种群间潜在形态分化的遗传机制。
