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案（公法111-5）资助的。什么机制使某些物种在热带森林中获得并保持较高的相对丰度，而其他物种却保持在低种群密度？这是生态学中的一个关键问题。虽然有许多理论解释，但很少有令人信服的实验证据支持。旱季优势假说是植物物种沿重要的环境梯度分布的一种新颖而简单的机制解释：降雨的变化。该假说认为，许多植物物种在季节性热带森林中获得高丰度是由于在季节性干旱时期获得的竞争优势，此时太阳辐射高，湿度有限，竞争物种处于休眠状态。由于大多数热带森林是季节性的，这一假设在世界范围内都具有相关性，而这一假设的基础思想可以扩展到任何经历季节性波动的生态系统。该项目将结合长期的生理和生长测量，对实验花园中的藤本植物（木本藤本植物）和树木以及沿着巴拿马地峡陡峭降雨梯度的永久林地进行测量。藤本植物特别重要，因为它们是热带森林的组成部分，在降雨较少的地区更为普遍，这种模式与旱季优势假说相一致。该项目将为一种简单的机制提供首批测试之一，该机制可以根据年平均降雨量控制植物物种的丰度和分布，年平均降雨量是世界各地一个现成的参数。本研究的广泛影响包括国际能力建设、学生指导和实地教育。该项目将积极招募和指导拉丁美洲的学生，其目标是为拉丁美洲科学家更多地参与塑造热带生态学领域提供一个模式。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，重点关注环境梯度对生物的基本限制。PI还将把该项目整合到他自己的巴拿马热带生态学课程中(威斯康星大学？教学生沿着这一重要的环境梯度比较和对比相关的植物和动物的适应性。

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.