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极度孤立，人们期待着一个独特的具有高度地方性的无脊椎动物底栖动物群。然而，构成底栖生物群落重要生态成分的一些无脊椎动物分类群包括40%以上的非特有物种(例如底栖多毛类)。为了解释非特有物种，南极和其他(例如南美洲)种群之间必须进行间歇性的遗传交换。这种基因流动的最有可能的机制，至少对于动物群内和流动的大型底栖动物来说，是浮游幼虫在亚南极和南极极锋上的扩散。为了测试幼虫的扩散作为维持极地锋面遗传连续性的一种机制，科学家们建议(1)在南半球夏季和冬季沿德雷克海峡的横断面采集浮游生物样本，同时收集适当的水文数据。这些数据将有助于阐明允许在德雷克海峡扩散的水文机制。使用分子系统学方法，他们将(2)比较来自南极和南美大陆的看似相同的成体形式，以确定遗传突变、历史上的基因流动以及对神秘物种的存在的控制。(3)类似的分子工具将被用来将浮游幼虫与其成虫联系起来。通过这一程序，他们建议将幼虫形态分别与它们来自南极或南美洲的幼虫联系起来。拟议的工作建立在先前研究的基础上，这些研究为综合理解南美/德雷克海峡/南极半岛地区历史上的基因流动和今天的扩散机制奠定了基础。此外，这项工作是首次尝试研究南极底栖无脊椎动物最近的基因流动。在这项研究期间，将对研究生和博士后进行培训。

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.