Historical and Contemporary Drivers of Macroalgal Reproductive System Variation along the Western Antarctic Peninsula

摘要：大多数生物在不同的生命阶段之间交替，这些阶段在染色体的数量和排列、细胞的数量以及最适合生存的环境条件上都有所不同。我们对这些交替的理解大部分来自动物和陆地植物等生物，其中一个阶段主导着生命周期，另一个阶段较小且短暂。然而，在整个生命之树中，有无数的生物体，它们的两个阶段都是长时间的，多细胞的，或者两者兼而有之。这些生命周期挑战了用来解释我们在自然界中看到的生态和进化模式的常见观点。大型藻类（海藻）显示了广泛的生命周期类型，因此是测试和扩展关于生命周期如何进化的想法的优秀模型。具有多种生命周期类型的海底海藻森林在南极半岛西部的浅水中占主导地位，在那里它们具有重要的生态意义，并且对大多数物种来说，位于其地理范围的南端。利用以前南极探险的现有样本，研究人员处于独特的位置，可以测试和扩展生命周期进化的知识，以及这与生殖模式变化的关系。该项目还将进一步实现国家科学基金会培养新一代科学家和向公众提供科学发现的目标。该项目将支持一名博士后学者和一名新加入美国南极研究的教员。研究人员将利用现有的一个项目，让高中生或本科生参与研究，这也将扩大博士后的指导经验。所有团队成员都将为专业协会为公众制作的博客撰写文章。技术摘要利用南极半岛西部沿纬度梯度分布的现有大型藻类分类群样本，探索其分布范围从中心到南纬向极限的遗传多样性模式。不仅将记录一个未被充分研究的关键南极生物群体的遗传多样性，而且还将探索它如何随着纬度的变化而变化，并结合高度的地方性特征。这将通过(i)表征许多物种遗传多样性的纬度梯度和（ii）确定五个焦点基础物种的生殖系统来实现。目前，大型藻类是世界沿海生态系统中主要的初级生产者，其遗传数据很少。这一差距在正在经历快速气候变化的南极海岸线上尤为明显。此外，南极洲被南大洋隔离，减少了从其他陆地块定期迁移的可能性。据预测，纬度上的生殖系统模式在很大程度上是由冰山冲刷和海冰覆盖变化导致的随纬度增加的再定居事件驱动的。因此，南极洲是了解孤立种群（包括许多地方性分类群）生殖模式变化背后的过程的最佳地点，同时扩展了我们对边缘环境如何与复杂生命周期相融合的认识。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

General abstractMost organisms alternate between life stages that vary in the number and arrangement of their chromosomes, in the number of cells they possess, and in the environmental conditions in which they are best adapted to live. Much of what we understand about these alternations comes from organisms like animals and land plants in which one of the two stages dominates the life cycle with the other small and short-lived. However, across the tree of life there are countless examples of organisms in which both stages are of long duration, multicellular, or both. These life cycles challenge common ideas used to explain ecological and evolutionary patterns we see in nature. Macroalgae (seaweeds) display a wide range of life cycle types and consequently are excellent models to test and expand ideas about how life cycles evolve. Undersea forests of seaweeds with a variety of life cycle types dominate the shallow waters of the western Antarctic Peninsula where they are ecologically important and, for most of the species, at the southern end of their geographic range. Using existing samples from previous expeditions to Antarctica, the investigators are uniquely positioned to test and expand knowledge of life cycle evolution and how this intersects with reproductive mode variation. This project will also further the NSF goals of training new generations of scientists and of making scientific discoveries available to the public. The project will support a postdoctoral scholar as well as a faculty member new to US Antarctic research. The investigators will take advantage of an existing program to include high school or undergraduate students in the work which will also expand mentorship experience for the postdoc. All team members will contribute by writing for blogs produced by professional societies for the public. Technical abstractExisting macroalgal taxa samples from across a latitudinal gradient in the western Antarctic Peninsula will be used to explore patterns of genetic diversity from the center to the southern latitudinal limits of their range. Not only will genetic diversity be documented for an understudied and critical group of Antarctic organisms, but how it changes with latitude, compounded by high levels of endemism, will be explored. This will be accomplished by (i) characterization of latitudinal gradients in genetic diversity of many species and (ii) determination of the reproductive system of five focal foundation species. At present, there are few genetic data for macroalgae, dominant primary producers in coastal ecosystems around the world. This gap is particularly acute along Antarctic coastlines that are experiencing rapid climate change. Furthermore, Antarctica is isolated by the Southern Ocean, decreasing the likelihood of regular migration from other land masses. Latitudinal reproductive system patterns are predicted to be largely driven by recolonization events that increase with latitude due to changes in iceberg scour and sea ice coverage. Thus, Antarctica is the best place to understand what processes underlie reproductive mode variation in populations that are isolated, including many endemic taxa, while simultaneously extending our knowledge about how marginal environments converge with complex life cycles.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.