Dissertation Research: Molecular mechanisms underlying rapid adaptive divergence in the Swamp Sparrow

论文研究：沼泽麻雀快速适应性分化的分子机制

• 批准号: 1501471
• 负责人: Irby Lovette
• 金额: $ 2.02万
• 依托单位: Cornell University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-07-01 至 2017-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1501471&HistoricalAwards=false
• 关键词: Dissertation; Research; Molecular; mechanisms; underlying

Populations of a single species that live in different geographic regions often diverge as natural selection drives adaptation to the local environment. Understanding the processes of divergence and local adaptation is of particular importance in this contemporary era of rapidly changing environments. The coastal salt marshes of North America provide excellent systems in which to study rapid adaptive divergence, given that these habitats have formed within the last 15,000 years and represent novel selective environments for their inhabitants. Within many independent lineages of birds, there is a strong pattern of evolving larger bills and darker plumage after colonizing coastal salt marshes, suggesting that these traits offer a selective advantage. This project will allow identification of the genetic basis of divergence in these traits, and provide a window into the evolutionary mechanisms underlying local adaptation. This project will also provide hands-on training for graduate and undergraduate students, and will provide useful information for the conservation of coastal bird populations. Two locally adapted subspecies of the Swamp Sparrow exist in the northeastern US: A brown inland form with a small bill, and a dark grey coastal form with a large bill. Preliminary DNA sequence (ddRAD) data reveal that the two forms are very similar, but several regions of the genome are highly differentiated between them. The natural history of coastal Swamp Sparrows suggests that strong directional selection may have influenced sequence variation in these highly differentiated regions. To test this hypothesis, patterns of genome-wide divergence will be surveyed by generating additional DNA sequence data for each differentiated region; these will be statistically examined for molecular signatures of selective sweeps. This project provides an important test of this emerging statistical methodology.

生活在不同地理区域的单一物种的种群往往因自然选择而分化，以适应当地环境。在这个环境迅速变化的当代，了解分化和局部适应的过程尤为重要。北美沿海的盐沼为研究快速适应性分化提供了很好的系统，因为这些栖息地是在过去的15000年里形成的，为它们的居民提供了新的选择环境。在许多独立的鸟类谱系中，在殖民沿海盐沼后，进化出更大的喙和更深的羽毛，这表明这些特征提供了一种选择优势。该项目将允许识别这些性状差异的遗传基础，并为当地适应的进化机制提供一个窗口。这个项目也将为研究生和本科生提供实践培训，并为保护沿海鸟类种群提供有用的信息。美国东北部有两种适应当地的沼泽麻雀亚种：一种是棕色的内陆麻雀，喙小，一种是深灰色的沿海麻雀，喙大。初步DNA序列（ddRAD）数据显示，这两种形式非常相似，但基因组的几个区域在它们之间高度分化。沿海沼泽麻雀的自然历史表明，强烈的方向选择可能影响了这些高度分化区域的序列变化。为了验证这一假设，将通过为每个分化区域生成额外的DNA序列数据来调查全基因组分化模式；这些将被统计检查选择性扫描的分子特征。这个项目为这种新兴的统计方法提供了重要的检验。