Collaborative Research: Evaluating Marine Clines to Predict Larval Retention

智力优点：尽管在推断海洋种群之间的基因流方面取得了巨大的分析进展，但仍然很难确定维持人口统计学空间变异或物种与浮游幼虫连通性的种群或机制。 人们对如何在看似混合良好的海洋系统中保留新的多样性知之甚少，特别是影响这些物种遗传变异模式的选择和扩散之间的平衡。 这项研究总体上探讨了不对称扩散对海洋多样性的影响，特别是对智利海岸沿线的藤壶 Notochthamalus scabrosus 的影响。 本质上，该研究的重点是洋流如何影响浮游幼虫的底栖无脊椎动物的地理地理和系统发育模式。 在该地区，该物种存在一个遗传谱系，可能代表藤壶的两个不同谱系之间基于性能的差异，以及近岸海洋学和潮间带生态学的转变。 将对幼虫扩散时允许该系持续存在的机制进行定量测试。 该研究将改善粗糙猪笼草的空间、时间和基因组特征，检查潜在的选择梯度，并将不对称基因流的间接估计器与连接物理海洋学和系统发育地理学的环境隔离模型进行比较。 这项研究将是对由 PI 开发的最新生物地理和种群遗传模型所做的预测的首次实证探索，这些模型对遗传结构在沿海海洋中持续存在的必要条件进行了预测。 该项目的独创性在于，不是仅仅依靠系统发育地理学推断来预测各种未经检验的假设下种群的连通性，而是结合物理和生物数据来确定维持沿海多样性的具体机制。 这项研究将维持粗糙猪笼草的动态与智利同事积极研究的其他海洋物种的模式联系起来，并将有助于验证当前对该海岸幼虫扩散的建模工作。 此外，与智利同事合作将有效获取和分析这项研究所需的数据。 对智利海岸的关注有很多好处，包括它与经过充分研究的俄勒冈州和加利福尼亚州海岸令人着迷的相似之处，可能允许从这项工作的结果中进行概括。 最重要的是，这项工作将把源汇动力学从理论文献推向人口统计模式如何在物种范围内分布和维持的基础研究，这对于理解范围限制本身的结构和动态具有重要意义。 这项工作将根据人口统计和基因流分析，结合海洋学特征，确定智利海岸沿线的可能来源种群，并提供一个可转移到任何海岸（例如美国太平洋海岸）沿线类似工作的框架，以澄清种群和物种范​​围限制的一般概念。更广泛的影响：粗糙猪笼草的转录组数据将成为节肢动物基因组比较分析的新资源。 这项研究将为扩大 PI、智利研究人员和学生之间的互动提供机会。 一名研究生和一名本科生（资金来自佐治亚大学的学生研究项目，特别是 URM）将参与该项目。 这项研究的所有产品将在适当的遗传 (NCBI) 和生态 (KNB) 数据库中公开提供。 这项工作预计将为海洋学和种群遗传数据的综合分析提供一个通用模型，以识别跨物种领域的人口统计模式。 这些方法可能适用于海洋保护区设计。 从本质上讲，了解维持沿海海洋系统发育地理多样性的机制将有助于在遗传和物种层面管理该生态系统及其多样性。

Intellectual Merits: Despite great analytical advances for inferring gene flow among marine populations, it is still difficult to identify the populations or mechanisms that maintain spatial variation in demography or connectivity in species with planktonic larvae. How novel diversity is retained in what appear to be well-mixed oceanic systems is poorly understood, particularly the balances between selection and dispersal that influence patterns of genetic variation in these species. This research explores effects of asymmetric dispersal on marine diversity, in general, and on the barnacle Notochthamalus scabrosus along the Chilean coast, in particular. Essentially, the study focuses on how currents influence geogeographic and phylogeograhic patterns of benthic invertebrates with planktonic larvae. In this region, there is a genetic cline of this species that may represent performance-based differences between two distinct lineages of the barnacle, and a transition in nearshore oceanography and intertidal ecology. The mechanisms that allow the cline to persist in the face of larval dispersal will be tested quantitatively. The research would improve the spatial, temporal, and genomic characterization of the cline in N. scabrosus, examine potential selection gradients, and compare indirect estimators of asymmetric gene flow with environmental isolation models that link physical oceanography and phylogeography. The study would be the first empirical exploration of predictions made by recent biogeographic and population-genetic models, developed by the PIs, of the conditions necessary for genetic structure to persist in the coastal ocean. The originality of this project is that instead of relying solely on phylogeographic inference to predict connectivity of populations under various untested assumptions, a combination of physical and biological data would be used to identify the specific mechanisms that maintain coastal diversity. This study would link the dynamics maintaining the N. scabrosus cline to patterns in other marine species actively studied by colleagues in Chile, and would help validate current modeling efforts of larval dispersal along that coast. Moreover, working with Chilean colleagues would be efficient for obtaining and analyzing data needed for this research. The focus on the Chilean coast has a number of benefits, including its intriguing similarity to the well-studied Oregon and California coasts, potentially allowing for generalizations from the results of this work. Most importantly, this work would push source-sink dynamics from the theoretical literature into basic research of how demographic patterns are distributed and maintained across a species' range, with implications for understanding the structure and dynamics of range limits themselves. The work would identify likely source populations along the Chilean coast based on demographic and gene flow analysis, in concert with oceanographic characteristics, and provide a framework transferable to similar efforts along any coast (e.g., Pacific coast of the US), towards clarifying general concepts of population and species range limits. Broader Impacts: Transcriptome data for N. scabrosus would be a new resource for comparative analysis of arthropod genomes. This research would provide opportunities for expanding interactions between the PIs, Chilean researchers and students. One graduate and one undergraduate student (funding leveraged from research programs for students, particularly URM, at U. Georgia) would participate in the project. All products of this research would be made publicly available in appropriate genetic (NCBI) and ecological (KNB) databases. The work is expected to provide a general model for combined analysis of oceanographic and population-genetic data to identify demographic patterns across a species' domain. These methods are likely to be applicable to marine reserve design. Essentially, understanding the mechanisms that maintain phylogeographic diversity in the coastal ocean would help efforts to manage this ecosystem and its diversity at the genetic and species levels.