Speciation and Gene Flow in the Open Ocean: the Phylogeography of an Oceanic Copepod Family

本项目将发展一个研究海洋全浮游动物种群物种形成的模型系统，以研究在开放海洋物种形成过程中重要的生物地理和生态因素。鱿鱼类桡足类Eucalanidae科分布于海洋，其组成物种可能完全是在开阔的海洋中进化而来的。这个科现存的23个物种将作为我们的模型系统。研究将由两部分组成。首先，基于一个线粒体（16s rDNA）和一个核（伸长因子-1-a）基因位点的物种水平分子系统发育将被开发，包括家族内所有已知的物种。姐妹种对将根据系统发育进行鉴定。关于这些姐妹物种对的比较生物地理分布、形态特征和遗传多样性，正在测试三个中心假设。结果将阐明生物地理范围重叠程度、后物种范围演化、生殖形态特征差异、生态特征差异和历史种群规模差异的模式。这样的结果将使我们深入了解在物种形成过程中起作用的那些因素。研究的第二部分是种内，将研究环全球透明桉和鼻鼻犀的遗传谱系的地理分布。这部分将确定海洋特征，这些特征在全球范围内为同种种群之间的基因流动创造了界限。种内单倍型网络将基于线粒体基因位点细胞色素氧化酶I （COI）产生。第二部分研究的目标是了解种群如何经历初始分化过程，这是物种形成模型的关键步骤。初步结果表明，所提出的工作具有巨大的潜在价值。在这个科中至少发现了三个以前隐藏的物种，并且目前对现有物种的生物地理分布的理解已经得到了修改。mtDNA分子系统发育的DNA测序工作已经完成了一半，所需的大部分标本也已经收集完毕。本研究的测序结果将存入GenBank，从而广泛传播给所有感兴趣的各方。拟进行的研究为博士研究。除了回答所提出的具体问题外，这项建议还将有助于培养具有系统学和现代分子技术能力的新一代海洋学家。

This project will develop a model system for the study of speciation in marine holozooplankton populations, to examine the biogeographic and ecological factors important during speciation in the open ocean. The calanoid copepod family Eucalanidae is oceanic in distribution, and component species are likely to have evolved entirely in the open ocean. The 23 extant species in this family will serve as our model system. The research will consist of two parts. First, a species level molecular phylogeny based on one mitochondrial (16s rDNA) and one nuclear (Elongation Factor-1-a) gene locus will be developed, including all known species within the family. Sister species pairs will be identified based on the phylogeny. Three central hypotheses are being tested regarding the comparative biogeographic distributions, morphological characteristics, and genetic diversity of these sister species pairs. Results will elucidate patterns in the extent of biogeographic range overlap, post-speciational range evolution, divergence in reproductive morphological characteristics, divergence in ecological characteristics, and differences in historical population sizes. Such results will provide insight into those factors that play a role in the speciation process. The second, intraspecific, part of the study will examine geographic distributions of genetic lineages in circumglobal Eucalanus hyalinus s.l. and Rhincalanus nasutus s.l. This component will identify oceanographic features that create boundaries to gene flow between conspecific populations on a global scale. Intraspecific haplotype networks will be generated based on the mitochondrial gene locus Cytochrome Oxidase I (COI). The goal of this second portion of the research is to understand how populations undergo the initial differentiation process, a step critical to speciation models. Initial results demonstrate the tremendous potential value of the proposed work. At least three previously cryptic species have been uncovered within the family, and current understanding of the biogeographic distributions of existing species has been modified. Half of the DNA sequencing for the mtDNA molecular phylogeny has been completed, and most of the specimens required for this work have already been collected. The sequences resulting from this research will be deposited in GenBank, and thus disseminated broadly to all interested parties. The proposed research is the doctoral study. In addition to answering the specific questions posed, this proposal will contribute to the training of a new generation of oceanographers with abilities in systematics and modern molecular techniques.