Dowell Stephanie A, Portik Daniel M, de Buffrénil Vivian, Ineich Ivan, Greenbaum Eli, Kolokotronis Sergios-Orestis, Hekkala Evon R
Department of Biological Sciences, Fordham University, 441 East Fordham Road, Bronx, NY 10458, United States.
Museum of Vertebrate Zoology, University of California, Berkeley, 3101 Valley Life Sciences Building, Berkeley, CA 94720, United States.
Mol Phylogenet Evol. 2016 Jan;94(Pt B):591-604. doi: 10.1016/j.ympev.2015.10.004. Epub 2015 Oct 22.
Previous studies of color pattern, tongue pigmentation, and scale counts have been used to distinguish two species of semiaquatic varanids in Africa, but these findings have yet to be tested with molecular data. The Varanus (Polydaedalus) niloticus Species Group is comprised of the Nile monitor (V. niloticus) and the Ornate monitor (V. ornatus). Due to the high rate of exploitation of both species for bushmeat, the leather industry, and the pet trade, a clear understanding of the taxonomy and genetic partitioning is necessary for effective management. Here we utilize a multilocus approach, consisting of mitochondrial and nuclear markers, totaling 4251 bp, as well as microsatellite loci to assess the taxonomic validity and intraspecific evolutionary patterns within the V. niloticus Species Group. By incorporating historical specimens from museum collections as well as contemporary samples, we obtained range-wide coverage for both species across Africa. Concordant results from various approaches all suggest that V. ornatus does not represent a distinct monophyletic group. Our analyses recovered three genetic clades within V. niloticus, representing western, northern, and southern lineages. The western clade was found to diverge first, around 7.7 mya (95% HPD: 4.6-11.0 mya) and exhibits 8.4% and 8.7% uncorrected sequence divergence between the northern and southern V. niloticus clades, respectively. This geographically separate lineage corresponds to previous descriptions of Tupinambis stellatusDaudin (1802). These findings not only call for taxonomic revision of this species group, but also shed light on the biogeographic history of Africa as well as aid in the management planning of varanids and other co-distributed African species.
先前关于色斑模式、舌色素沉着和鳞片计数的研究已被用于区分非洲的两种半水生巨蜥，但这些研究结果尚未通过分子数据进行验证。尼罗巨蜥物种组（Varanus [Polydaedalus] niloticus Species Group）由尼罗河巨蜥（V. niloticus）和华丽巨蜥（V. ornatus）组成。由于这两个物种在丛林肉、皮革工业和宠物贸易中都被大量利用，因此，为了进行有效管理，清楚了解其分类学和遗传划分是必要的。在此，我们采用多基因座方法，包括线粒体和核标记（共4251碱基对）以及微卫星基因座，以评估尼罗巨蜥物种组内的分类学有效性和种内进化模式。通过纳入博物馆收藏的历史标本以及当代样本，我们获得了这两个物种在非洲范围内的广泛覆盖。各种方法得出的一致结果均表明，华丽巨蜥并不代表一个独特的单系类群。我们的分析在尼罗河巨蜥中发现了三个遗传分支，分别代表西部、北部和南部谱系。发现西部谱系最早分化，大约在770万年前（95%最高后验密度区间：460 - 1100万年前），并且在尼罗河巨蜥北部和南部谱系之间分别表现出8.4%和8.7%的未校正序列差异。这个地理上隔离的谱系与之前对杜丁氏星斑巨蜥（Tupinambis stellatus Daudin，1802年）的描述相对应。这些发现不仅要求对该物种组进行分类学修订，还为非洲的生物地理历史提供了线索，并有助于巨蜥及其他同域分布的非洲物种的管理规划。
