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

由于自渐新世早期以来南极大陆极度孤立，人们期待着一种独特的、具有高度特有性的底栖无脊椎动物群。然而，一些构成沉积底栖群落重要生态成分的无脊椎动物类群包括 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）种群之间必须发生间歇性基因交换。这种基因流动最可能的机制，至少对于动物体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的扩散。为了测试幼虫扩散作为维持极地锋面遗传连续性的机制，科学家们建议（1）在南半球夏季和冬季沿德雷克通道横断面采集浮游生物样本，同时收集适当的水文学数据。这些数据将有助于阐明允许跨越德雷克海峡扩散的水文学机制。他们将使用分子系统发育方法（2）比较来自南极洲和南美洲大陆的看似相同的成虫形式，以识别遗传断裂、历史基因流动以及对神秘物种存在的控制。 (3) 类似的分子工具将用于将浮游幼虫与其成虫联系起来。通过这个程序，他们建议将幼虫形态分别与其南极或南美洲起源联系起来。拟议的工作建立在先前的研究基础上，为对南美/德雷克海峡/南极半岛地区历史基因流和当今传播机制的综合理解提供了基础。此外，这项工作代表了研究南极底栖无脊椎动物近期基因流的首次尝试之一。研究生和博士后将在这项研究期间接受培训。

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.