Collaborative Research: Relevance of Planktonic Larval Dispersal to Endemism and Biogeography of Antarctic Benthic Invertebrates

由于早渐新世以来，南极大陆与外界极度隔绝，人们期望这里有一种独特的、具有高度地方性的无脊椎底栖动物群。然而，一些构成沉积底栖生物群落重要生态组成部分的无脊椎动物类群包括40%以上的非地方性物种（如底栖多毛类）。为了解释非地方性物种，必须在南极和其他（如南美）种群之间进行间歇性的遗传交换。这种基因流动最可能的机制，至少对于动物群内和移动的大型底栖动物来说，是浮游生物幼虫在亚南极和南极极地锋的扩散。为了测试幼虫扩散作为一种维持极地锋遗传连续性的机制，科学家们建议(1)在南部夏季和冬季沿着德雷克海峡的样带采集浮游生物样本，同时收集适当的水文数据。这些数据将有助于阐明通过德雷克海峡扩散的水文机制。使用分子系统发育方法，他们将(2)比较来自南极和南美大陆的看似相同的成年形式，以确定遗传断裂、历史基因流动和对隐藏物种存在的控制。(3)将使用类似的分子工具来将浮游生物幼虫与它们的成虫联系起来。通过这个程序，他们建议将幼虫形式分别与它们的南极或南美洲起源联系起来。提出的工作建立在先前的研究基础上，为这一努力提供了基础，以发展对南美洲/德雷克海峡/南极半岛地区历史基因流动和当今扩散机制的综合理解。此外，这项工作是研究南极底栖无脊椎动物近期基因流动的首次尝试之一。本研究将培养研究生和一名博士后。

Because of extreme isolation of the Antarctic continent since the Early Oligocene, one expects a unique invertebrate benthic fauna with a high degree of endemism. Yet some invertebrate taxa that constitute important ecological components of sedimentary benthic communities include more than 40 percent non-endemic species (e.g., benthic polychaetes). To account for non-endemic species, intermittent genetic exchange must occur between Antarctic and other (e.g. South American) populations. The most likely mechanism for such gene flow, at least for in-faunal and mobile macrobenthos, is dispersal of planktonic larvae across the sub- Antarctic and Antarctic polar fronts. To test for larval dispersal as a mechanism of maintaining genetic continuity across polar fronts, the scientists propose to (1) take plankton samples along transects across Drake passage during both the austral summer and winter seasons while concurrently collecting the appropriate hydrographic data. Such data will help elucidate the hydrographic mechanisms that allow dispersal across Drake Passage. Using a molecular phylogenetic approach, they will (2) compare seemingly identical adult forms from Antarctic and South America continents to identify genetic breaks, historical gene flow, and control for the presence of cryptic species. (3) Similar molecular tools will be used to relate planktonic larvae to their adult forms. Through this procedure, they propose to link the larval forms respectively to their Antarctic or South America origins. The proposed work builds on previous research that provides the basis for this effort to develop a synthetic understanding of historical gene flow and present day dispersal mechanism in South American/Drake Passage/Antarctic Peninsular region. Furthermore, this work represents one of the first attempts to examine recent gene flow in Antarctic benthic invertebrates. Graduate students and a postdoctoral fellow will be trained during this research.