Integrated Adaptations to Moisture Supply and Cross-over in Whole-plant Growth among Eucalyptus Species Along an Australian Rainfall Gradient

陆地植物面临着一个基本的权衡：为了获得光合作用和生长所需的二氧化碳，它们必须将潮湿的活细胞暴露在干燥的大气中，这将导致大量的水分损失。任何减少水分流失的调整都是以减缓碳的摄入为代价的。理论表明，为了最大限度地提高整个植株的生长和存活率，大约20个涉及植物形态、生理和叶片结构的性状应该随水分供应而变化。这项研究将检查10种桉树（地球上种植最广泛的树木属之一）的所有这些特征，这些特征在澳大利亚维多利亚州从温带雨林到半沙漠的降雨梯度中分布不同。植物将在跨越这一坡度的四个普通花园中种植。光合作用和水运输能力的测量将定期进行，定期收获将用于评估形态和生长速度。这个项目是理解适应湿度供应的先驱，因为它结合了一种新的理论方法和使用普通花园来测试塑造物种分布的潜在力量。本项目将培养1名博士后、至少1名研究生和多名本科生。研究结果将有助于了解植物对长期和严重干旱的响应及其在干旱地区的分布。关于桉树适应水分供应的多媒体演示将在公共电视上播出，威斯康星大学麦迪逊分校和悉尼大学将提供一个重点关注植物适应和群落生态学的顶级实地课程。在澳大利亚维多利亚州的10个桉树物种中，通过系统发育分层和连续年降雨量的优势，研究了涉及光合作用、水力和资源分配的大约20个性状的植物生存、生长、适应和整合。测量将在跨越这一坡度的四个普通花园进行两次为期两年的实验。将进行适应和功能整合的系统发育结构测试，询问观察到的变化是否倾向于使高度增长率最大化，物种内部对水分供应的可塑性模式是否与物种之间的模式相冲突，以及物种是否显示适应性交叉的证据，分类群在高度生长或生存方面具有优势，只有在与它们在自然界中占主导地位的条件相似的情况下才能生存。对每个普通花园竞争成功的直接实验测试将与基于非拥挤单一栽培的增长率的预期和基于植物特性的理论预测进行比较。在研究植物对水分供应的适应性方面，本研究是新颖的，包括研究植物对水分供应的适应性和整合的特征范围，利用普通花园来测试高度生长的交叉，作为适应的支持和塑造物种分布的潜在力量，以及使用生长模型来确定影响植物生长的关键性状和性状集合。

Land plants face a fundamental tradeoff: to acquire the carbon dioxide needed to photosynthesize and grow, they must expose their moist, living cells to a dry atmosphere, which causes enormous losses of water. Any adjustment to minimize water loss comes at the price of slower intake of carbon. Theory suggests that roughly 20 traits involving plant morphology, physiology, and leaf structure should vary with moisture supply in order to maximize whole-plant height growth and survival. This study will examine all these traits in ten species of Eucalyptus (one of the most widely planted genera of trees on Earth) that differ in their distribution across a rainfall gradient from temperate rain forest to semi-desert in Victoria, Australia. Plants will be grown in four common gardens that span this gradient. Measurements of photosynthetic and water transport capacity will be made regularly and periodic harvests will be used to assess morphology and rates of growth. This project is pioneering for understanding adaptation to moisture supply, because it combines a novel theoretical approach with the use of common gardens to test for potential forces shaping species distributions. This project will train a postdoc, at least one graduate student, and multiple undergraduates. The results will help to understand plant response to prolonged and severe droughts, and distribution in arid regions. A multimedia presentation on Eucalyptus adaptation to moisture supply will be made for public television, and a capstone field course will be offered through UW-Madison and U Sydney that will focus on plant adaptation and community ecology.Plant survival, growth, adaptation, and integration of roughly 20 traits involving photosynthesis, hydraulics, and resource allocation will be studied in ten Eucalyptus species, stratified phylogenetically and by dominance of successive bands of annual rainfall in Victoria, Australia. Measurements will be made over two 2-year experiments at four common gardens spanning this gradient. Phylogenetically structured tests of adaptation and functional integration will be conducted, asking whether the observed shifts tend to maximize rates of height growth, whether patterns of plasticity within species in response to moisture supply conflict with those seen across species, and whether species show evidence of adaptive cross-over, with taxa having an advantage in height growth or survival only under conditions similar to those they dominate in nature. A direct experimental test of competitive success at each common garden will be compared with expectations based on growth rates of uncrowded monocultures and theoretical predictions based on plant traits. The proposed research is novel for studying plant adaptation to moisture supply, in terms of the range of traits whose adaptation and integration will be examined, the use of common gardens to test for cross-over in height growth as support for adaptation and a potential force shaping species distributions, and the use of growth models to identify key traits and trait aggregates that affect plant growth.