Jennings Robert M, Shank Timothy M, Mullineaux Lauren S, Halanych Kenneth M
Biology Department, University of Massachusetts at Boston, 100 Morrissey Boulevard, Boston, MA 02125, USA.
J Hered. 2009 Jan-Feb;100(1):86-96. doi: 10.1093/jhered/esn067. Epub 2008 Sep 11.
Previous genetic studies suggest Cape Cod, MA, as a phylogenetic break for benthic marine invertebrates; however, diffuse sampling in this area has hindered fine-scale determination of the break's location and underlying causes. Furthermore, some species exhibit breaks in different places, and others exhibit no breaks in this region. We analyze the phylogeographic patterns of 2 mitochondrial genes from 10 populations of the bamboo worm Clymenella torquata (Annelida: Maldanidae) focused around Cape Cod but extending from the Bay of Fundy, Canada, to New Jersey. A common invertebrate along the US coast, C. torquata, possesses life-history characteristics that should make it sensitive to factors such as dispersal barriers, bottlenecks, and founder events. As an inhabitant of soft sediments, C. torquata offers a unique contrast to existing research dominated by organisms dwelling on hard substrates. Our genetic data show a clear phylogenetic break and a cline of haplotype frequencies from north to south. Fine-scale sampling of populations on Cape Cod, combined with other sampled populations, confirm that this distinct break is not on the Cape Cod peninsula itself but to the south near a boundary of oceanic water masses. Low levels of gene flow occur in these populations, in an asymmetric manner congruent with coastal current patterns. No significant effect of Pleistocene glaciation was seen in the pattern of genetic diversity over the sampled range.
先前的遗传学研究表明，马萨诸塞州的科德角是底栖海洋无脊椎动物的系统发育断点；然而，该地区的分散采样阻碍了对断点位置及其潜在原因的精细确定。此外，一些物种在不同地点出现断点，而其他物种在该地区则没有断点。我们分析了来自10个竹虫Clymenella torquata（环节动物门：马尔丹科）种群的2个线粒体基因的系统地理模式，这些种群集中在科德角周围，但从加拿大芬迪湾延伸至新泽西州。作为美国海岸常见的无脊椎动物，C. torquata具有的生活史特征使其应对诸如扩散障碍、瓶颈效应和奠基者事件等因素敏感。作为软质沉积物的栖息者，C. torquata与以硬底物上栖息生物为主的现有研究形成了独特对比。我们的遗传数据显示出明显的系统发育断点以及单倍型频率从北到南的渐变群。对科德角种群的精细采样，结合其他采样种群，证实这个明显的断点不在科德角半岛本身，而是在其南部靠近海洋水体边界的地方。这些种群中基因流水平较低，且以与沿岸海流模式一致的不对称方式发生。在采样范围内的遗传多样性模式中未观察到更新世冰川作用的显著影响。
