CAREER: Explaining the Distribution and Dominance of Lianas and Tree Species - A Test of the Dry Season Advantage Hypothesis

该奖项是根据2009年《美国复苏和再投资法》(公法111-5)资助的。是什么机制允许一些物种在热带森林中获得并保持较高的相对丰度，而其他物种则保持在低种群密度？这是生态学中的一个关键问题。尽管有许多理论解释，但很少有实验证据令人信服地支持这一点。旱季优势假说是一种新颖而简单的机制，解释了植物物种沿着一个重要的环境梯度的分布：降雨量的变化。该假说指出，许多植物物种在季节性热带森林中获得高丰度，是因为在季节性干旱期间，当太阳辐射高，湿度有限，竞争物种处于休眠状态时，生长获得了竞争优势。因为大多数热带森林都是季节性的，所以这一假说在世界范围内都具有相关性，而且该假说背后的想法可以扩展到任何经历季节性波动的生态系统。PI将结合对实验花园和沿巴拿马地峡陡峭降雨梯度的永久林地中的藤本植物(木本藤本植物)和树木的长期生理和生长测量。藤本植物特别重要，因为它们是热带森林的组成部分，在降雨量较少的地区更为普遍，这一模式符合旱季优势假说。该项目将提供对一种简单机制的首批测试之一，这种机制可以根据平均年降雨量控制植物物种的丰度和分布，这是世界各地地点随时可以获得的参数。这项研究的更广泛影响包括国际能力建设、学生指导和实地教育。该协会将积极招募和指导拉丁美洲学生，目的是为拉丁美洲科学家更多地参与热带生态领域的塑造提供一个模式。该项目为北美研究生和本科生的论文研究提供了基础设施，重点是对环境梯度对生物体施加的基本限制。PI还将把该项目整合到他自己的巴拿马热带生态学课程(威斯康星大学密尔沃基分校)，教学生比较和对比沿着这一重要环境梯度的相关植物和动物的适应。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).What mechanisms allow some species to attain and maintain high relative abundance in tropical forests, while other species remain at low population densities? This is a key question in ecology. Although there are a number of theoretical explanations, few have been convincingly supported by experimental evidence. The dry season advantage hypothesis is a novel and simple mechanistic explanation for the distribution of plant species along an important environmental gradient: the change in rainfall. The hypothesis states that many plant species attain high abundance in seasonal tropical forests due to the competitive advantage gained from growth during seasonal drought, when solar radiation is high, moisture is limiting, and competing species are dormant. Because most tropical forests are seasonal, the hypothesis has relevance worldwide, and the ideas underlying the hypothesis can be extended to any ecosystem that experiences seasonal fluctuations. The PI will use a combination of long-term physiological and growth measurements on lianas (woody vines) and trees in experimental gardens and in permanent forest plots along a steep rainfall gradient across the Isthmus of Panama. Lianas are of particular importance because they are integral components of tropical forests and are more prevalent in areas that have less rainfall, a pattern that is consistent with the dry season advantage hypothesis. The project will provide one of the first tests of a simple mechanism that may control the abundance and distribution of plant species based on mean annual rainfall, a readily available parameter for sites around the world. Broader impacts of this research include international capacity building, student mentoring, and field-based education. The PI will actively recruit and mentor Latin American students with the goal of providing a model for increasing participation of Latin American scientists in shaping the field of tropical ecology. The project provides the infrastructure for North American graduate and undergraduate student thesis research focusing on fundamental constraints imposed on organisms over environmental gradients. The PI will also integrate the project into his own Tropical Ecology in Panama course (University of Wisconsin?Milwaukee) to teach students to compare and contrast relevant plant and animal adaptations along this important environmental gradient.