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

大多数生物体在不同的生命阶段之间交替，这些生命阶段在染色体的数量和排列、细胞的数量以及它们最适合生存的环境条件方面都有所不同。我们对这些变化的理解大部分来自动物和陆地植物等生物体，其中两个阶段之一在生命周期中占主导地位，另一个阶段很小，寿命很短。然而，在整个生命树中，有无数的例子表明，生物体的两个阶段都是长期的，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，因此是测试和扩展生命周期如何演变的想法的绝佳模型。在南极半岛西部的浅水沃茨，海底海藻林具有各种生命周期类型，在那里它们具有重要的生态意义，而且对大多数物种来说，它们位于其地理范围的南端。利用以前南极考察的现有样本，研究人员处于独特的地位，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异的交叉。该项目还将进一步推动NSF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以及一名新的美国南极研究教员。调查人员将利用现有的计划，包括高中或本科生的工作，这也将扩大博士后导师的经验。所有团队成员都将为专业协会为公众制作的博客撰稿。 技术摘要现有的大型藻类类群样品横跨纬度梯度在南极洲西部半岛将被用来探索从中心到南部纬度限制其范围的遗传多样性模式。不仅将记录南极生物的遗传多样性，而且还将探索它如何随着纬度的变化而变化，并伴随着高度的特有性。这将通过（一）描述许多物种遗传多样性的纬度梯度和（二）确定五个重点基础物种的生殖系统来实现。目前，世界各地沿海生态系统中占主导地位的初级生产者大型藻类的遗传数据很少。这一差距在沿着正在经历快速气候变化的南极海岸线尤为严重。此外，南极洲被南大洋孤立，减少了从其他大陆块定期移徙的可能性。垂直生殖系统模式预计将在很大程度上是由于冰山冲刷和海冰覆盖率的变化而导致的随纬度增加的电离事件。因此，南极洲是了解孤立种群（包括许多地方性类群）生殖模式变异背后的过程的最佳地点，同时也扩展了我们关于边缘环境如何与复杂生命周期汇合的知识。该奖项反映了NSF的法定使命，并被认为值得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来支持。

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.