RUI: Collaborative Research: Trait differentiation and local adaptation to depth within meadows of the foundation seagrass Zostera marina

了解物种如何应对其环境的空间变化（例如光和温度的梯度）对于知情管理以及预测它们如何应对变化是必要的。该项目将研究普通大叶藻（Zostera marina）的关键性状如何随深度变化，大叶藻是全球温带近岸生态系统中最重要的基础物种之一。研究人员将结合现场和实验室的实验，结合精细的分子分析，确定海草性状变异的遗传和环境因素。这项工作将为基础物种在可变环境中持续存在的微观进化机制提供重要信息，从而推动整个近岸群落的生态功能。该项目支持的东北大学研究生和基恩州立学院（KSC）本科生将接受最先进的分子技术培训，以及科学交流和推广方面的指导和经验。KSC学生的很大一部分来自科学领域代表性不足的群体。该研究的主要发现将被纳入本科课程和面向代表性不足群体的高中生的推广计划，并在地方和国家科学家和利益相关者会议上发表。本地适应，即“本地”基因型与“外来”基因型在本地环境中的优越表现，有力地证明了自然选择如何克服基因流动和漂移，从而形成与环境相匹配的表型。检验本地适应性的经典方法是互惠移植。然而，这样的实验往往不能捕捉到移民过程的关键方面，这些方面可能介导了自然系统中已实现的基因流动。例如，互惠移植实验通常在同一（通常是成年）生活史阶段测试本地和非本地表型，并且在相同的丰度或密度下，这并不能反映大多数物种的实际扩散情况。在实际人口中，移民（非本地）的数量往往低于居民（本地），相对频率本身会影响适应性。特别是，罕见的表型可能会经历资源竞争减少，或从专门的病原体相对释放。这种负频率依赖选择可以减少迁徙者和居民之间因局部适应而产生的适应度差异，放大有效基因流动，从而保持更大的种群内遗传多样性。研究人员将结合空间配对采样和精细尺度的分子分析，将6个草甸的种子/幼苗性状在深度梯度上的变化与可能驱动这些模式的关键因素联系起来：当地环境条件、人口统计和基因在深度上的流动。然后，研究小组将在生态相关的背景下通过实验测试交叉梯度扩散的结果，方法是从不同的深度相互播种种子，并操纵与成虫和其他幼苗谱系相关的相对频率。当地适应和频率依赖之间可能的相互作用与滨海Zostera marina特别相关，它代表了遗传多样性和身份的生态影响的最佳记录例子之一。此外，更好地了解海草的性状分化不仅是一个学术问题，而且对海草的成功恢复和保护至关重要。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。

Understanding how species cope with spatial variation in their environment (e.g. gradients in light and temperature) is necessary for informed management as well as for predicting how they may respond to change. This project will examine how key traits vary with depth in common eelgrass (Zostera marina), one of the most important foundation species in temperate nearshore ecosystems worldwide. The investigators will use a combination of experiments in the field and lab, paired with fine-scale molecular analyses, to determine the genetic and environmental components of seagrass trait variation. This work will provide important information on the microevolutionary mechanisms that allow a foundation species to persist in a variable environment, and thus to drive the ecological function of whole nearshore communities. The Northeastern University graduate and Keene State College (KSC) undergraduate students supported by this project will receive training in state-of-the-art molecular techniques, as well as mentorship and experience in scientific communication and outreach. A significant portion of KSC students are from groups under-represented in science. Key findings of the research will be incorporated into undergraduate courses and outreach programs for high school students from under-represented groups, and presented at local and national meetings of scientists and stakeholders. Local adaptation, the superior performance of "home" versus "foreign" genotypes in a local environment, is a powerful demonstration of how natural selection can overcome gene flow and drift to shape phenotypes to match their environment. The classic test for local adaptation is a reciprocal transplant. However, such experiments often fail to capture critical aspects of the immigration process that may mediate realized gene flow in natural systems. For example, reciprocal transplant experiments typically test local and non-local phenotypes at the same (often adult) life history stage, and at the same abundance or density, which does not mirror how dispersal actually occurs for most species. In real populations, migrants (non-local) often arrive at low numbers compared to residents (local), and relative frequency itself can impact fitness. In particular, rare phenotypes may experience reduced competition for resources, or relative release from specialized pathogens. Such negative frequency dependent selection can reduce fitness differences between migrants and residents due to local adaptation, and magnify effective gene flow, thus maintaining greater within-population genetic diversity. The investigators will combine spatially paired sampling and fine-scale molecular analyses to link seed/seedling trait variation across the depth gradient at six meadows to key factors that may drive these patterns: local environmental conditions, population demography, and gene flow across depths. The team will then experimentally test the outcome of cross-gradient dispersal in an ecologically relevant context, by reciprocally out-planting seeds from different depths and manipulating relative frequency in relation to both adults and other seedling lineages. The possible interaction between local adaptation and frequency-dependence is particularly relevant for Zostera marina, which represents one of the best documented examples of the ecological effects of genetic diversity and identity. Further, a better understanding of seagrass trait differentiation is not simply a matter of academic interest, but critical to successful seagrass restoration and conservation.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.