Collaborative research: ENSO-enhanced gene flow across the Eastern Pacific Barrier

合作研究：ENSO 增强了跨越东太平洋屏障的基因流

• 批准号: 0550294
• 负责人: Iliana Baums
• 金额: $ 26.27万
• 依托单位: Pennsylvania State Univ University Park
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-07-15 至 2010-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0550294&HistoricalAwards=false
• 关键词: Collaborative; research; ENSO; enhanced; gene

Coral reefs constitute the world's most-species-rich marine ecosystems, but anthropogenic changes threaten their health and jeopardize economies that depend on them. Populations of corals living in the eastern Pacific Ocean are especially precarious, as they inhabit a region where environmental conditions already dictate a marginal existence and they are isolated from other Pacific reef corals by 5000-8000 km of uninhabitable deep water (the Eastern Pacific Barrier, EPB). Managing these corals requires knowledge of which populations share common evolutionary histories and how dispersal presently links populations. This information has gone lacking because 1) the mitochondrial DNA markers often used to infer population relationships have proven invariant within coral species and thus uninformative, and 2) genetic analyses based on allele frequency data estimate migration averaged over thousands of generations, which may not reflect present patterns of population connectivity. Recent increases in the intensity of El-Nino Southern Oscillation (ENSO) events may have altered patterns of inter-population dispersal over the last few generations. Such ENSO events halve the eastward transport time of propagules traveling from luxuriant central Pacific coral reefs to the eastern Pacific. This project will employ a combination of genetic techniques to determine 1) when populations of corals in the eastern Pacific diverged from those in the central Pacific, 2) how present-day coral populations in these regions are linked by dispersal, and 3) whether recent changes in currents caused by ENSO events have altered these patterns of exchange. Critical to the success of the work will be the application of new genetic analyses designed to recognize groups of populations that have been isolated only very recently (20 generations) and can reveal past changes in population sizes. The work will focus on a major Pacific reef builder, Porites lobata. Samples of about 40 individuals will be made from each of 12 localities spanning the EPB. Alternative hypotheses for divergence times will be evaluated by comparing the distribution of monophyletic and paraphyletic gene genealogies to modeled expectations and by using coalescent analyses. Nuclear gene sequences from 15 single copy loci (obtained from random sampling of cDNA libraries) will be used for this purpose. Microsatellite loci (12-15 per species) will provide multi-locus genotypes for input into model-based clustering and assignment programs. These genetic analyses will provide a picture of how migration presently connects central and eastern Pacific corals and whether and how changes in ENSO events have altered these patterns. The genetic data to be gathered here will provide critical information for managing a natural resource upon which many people depend. The proposed research will provide training opportunities to undergraduate and graduate students at an institution that serves a region with a large minority population.

珊瑚礁是世界上物种最丰富的海洋生态系统，但人为变化威胁着它们的健康，并危及依赖它们的经济。生活在东太平洋的珊瑚种群特别不稳定，因为它们居住的区域的环境条件已经决定了它们的边缘存在，并且它们与其他太平洋珊瑚礁珊瑚隔离在5000-8000公里的不适合居住的深水中（东太平洋屏障，EPB）。管理这些珊瑚需要了解哪些种群具有共同的进化历史，以及目前的扩散如何将种群联系起来。这方面的信息已经缺乏，因为1）线粒体DNA标记通常用于推断种群关系已被证明在珊瑚物种中是不变的，因此没有信息，2）基于等位基因频率数据的遗传分析估计了数千代的平均迁移，这可能无法反映目前的种群连接模式。最近厄尔尼诺南方涛动（ENSO）事件强度的增加可能改变了过去几代人的种群间扩散模式。这种ENSO事件使繁殖体从繁茂的中太平洋珊瑚礁向东运输到东太平洋的时间减半。该项目将采用一系列遗传技术，以确定：（1）东太平洋珊瑚种群何时与中太平洋珊瑚种群发生分化;（2）这些区域目前的珊瑚种群如何通过扩散联系在一起;（3）最近厄尔尼诺/南方涛动事件引起的洋流变化是否改变了这些交换模式。这项工作取得成功的关键将是应用新的遗传分析，以识别最近（20代）才被隔离的种群，并能揭示过去种群规模的变化。这项工作将集中在一个主要的太平洋珊瑚礁建设者，滨珊瑚lobata。将从跨越EPB的12个地点中的每一个地点抽取大约40个人的样本。分歧时间的替代假设将通过比较单系和并系基因谱系的分布与建模预期以及使用合并分析来评估。来自15个单拷贝基因座的核基因序列（从cDNA文库随机取样获得）将用于此目的。微卫星位点（每个物种12-15个）将提供多位点基因型，用于输入基于模型的聚类和分配程序。这些遗传分析将提供一幅图片，说明目前迁移如何将太平洋中部和东部珊瑚联系起来，以及厄尔尼诺/南方涛动事件的变化是否以及如何改变了这些模式。在这里收集的遗传数据将为管理许多人赖以生存的自然资源提供重要信息。拟议的研究将为本科生和研究生提供培训机会，在一个服务于少数民族人口众多的地区的机构。