SG: Ecological insights from range-expanding populations

随着大气和海洋变暖，动植物正在扩大它们的地理分布。例如，招潮蟹最近将其活动范围扩大到马萨诸塞州科德角的历史极限以北。虽然科学家们已经记录了数千种物种的活动范围扩大，但一个大问题仍然存在：这些生物对它们在扩大的活动范围内占据的新栖息地有什么影响？招潮蟹生活在盐沼中，这是经济上重要的生态系统，为渔业和旅游业提供了动力。这项研究将重点关注招潮蟹对新扩大范围（即科德角以北）的盐沼的影响。该项目的调查结果将向公众公布。除本科生和研究生外，中学师生将直接参与本研究。有记载的招潮蟹（Uca pugnax）向北扩张是一个绝佳的机会，可以测试气候驱动的物种引入对生态系统功能的影响。在其原生地，蒲公英影响沼泽的一系列功能，包括初级生产、养分循环和食物网。就体型而言，招潮蟹遵循伯格曼法则（体型与纬度呈正相关），马萨诸塞州的个体几乎是乔治亚州个体的两倍。这种生物地理格局可能为气候变化背景下个体种群对生态系统功能的相对影响提供信息。本研究将检验以下假设：(1)扩大范围种群（如马萨诸塞州）中的招潮蟹对沼泽功能的人均影响将大于历史范围种群（如佐治亚州）中的招潮蟹，因为它们的体积更大。(2)。在景观尺度上，范围扩大的螃蟹相对于历史范围的螃蟹对沼泽功能的影响较小，因为这些种群比历史范围的种群小10倍。这些假设将通过沿着纬度梯度（乔治亚州、弗吉尼亚州、马萨诸塞州）对一套生态系统过程（如初级生产、分解、底栖动物多样性、植物化学计量学）的实地实验和观测研究相结合进行检验。此外，将在中生态系统研究中验证招潮蟹体型与生态系统影响相关的目标假设。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。

As the atmosphere and oceans warm, plants and animals are expanding their geographic distributions. For instance, the fiddler crab recently expanded its range north of its historic limit of Cape Cod, Massachusetts. While scientists have documented the range expansion of thousands of species, a big question remains: What is the impact of these organisms on the new habitats they occupy in their expanded ranges? Fiddler crabs live in salt marshes, which are economically important ecosystems that fuel fisheries and tourism. This research will focus on the impact that fiddler crabs will have on salt marshes in the newly expanded range (i.e., north of Cape Cod). Findings from this project will be made available to the public. Middle-school teachers and students in addition to undergraduate and graduate students will be directly involved in this research. The documented northern expansion of fiddler crabs (Uca pugnax) is an exceptional opportunity to test the effects of climate-driven species introductions on ecosystem functioning. In its native range, U. pugnax influences a range of marsh functioning including primary production, nutrient cycling, and food-webs. In terms of body size, fiddler crabs follow Bergmann's Rule (a positive relationship between body size and latitude) with individuals in Massachusetts being almost twice as large as those in Georgia. This biogeographic pattern may inform the relative effect of individual populations on ecosystem function in the context of climate change. The following hypotheses will be tested in this study: (1.) Fiddler crabs in the expanded-range populations (e.g., Massachusetts) will have larger per-capita effects on marsh functioning than those in the historic-range populations (e.g., Georgia) because of their larger size. (2.) At the landscape-scale, range-expanded crabs will have minor effects on marsh functioning relative to historic crabs because these populations are 10x smaller than historic-range populations. These hypotheses will be tested using a combination of field experiments and observational studies along a latitudinal gradient (Georgia, Virginia, Massachusetts) on a suite of ecosystem processes (e.g., primary production, decomposition, benthic animal diversity, plant stoichiometry). In addition, the targeted hypothesis that fiddler crab body size is correlated with ecosystem impacts will be tested in a mesocosm study.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.