Angert Amy L, Huxman Travis E, Chesson Peter, Venable D Lawrence
Department of Biology, Colorado State University, Fort Collins, CO 80523, USA.
Proc Natl Acad Sci U S A. 2009 Jul 14;106(28):11641-5. doi: 10.1073/pnas.0904512106. Epub 2009 Jul 1.
How biological diversity is generated and maintained is a fundamental question in ecology. Ecologists have delineated many mechanisms that can, in principle, favor species coexistence and hence maintain biodiversity. Most such coexistence mechanisms require or imply tradeoffs between different aspects of species performance. However, it remains unknown whether simple functional tradeoffs underlie coexistence mechanisms in diverse natural systems. We show that functional tradeoffs explain species differences in long-term population dynamics that are associated with recovery from low density (and hence coexistence) for a community of winter annual plants in the Sonoran Desert. We develop a new general framework for quantifying the magnitude of coexistence via the storage effect and use this framework to assess the strength of the storage effect in the winter annual community. We then combine a 25-year record of vital rates with morphological and physiological measurements to identify functional differences between species in the growth and reproductive phase of the life cycle that promote storage-effect coexistence. Separation of species along a tradeoff between growth capacity and low-resource tolerance corresponds to differences in demographic responses to environmental variation across years. Growing season precipitation is one critical environmental variable underlying the demographic decoupling of species. These results demonstrate how partially decoupled population dynamics that promote local biodiversity are associated with physiological differences in resource uptake and allocation between species. These results for a relatively simple system demonstrate how long-term community dynamics relate to functional biology, a linkage scientists have long sought for more complex systems.
生物多样性是如何产生和维持的，这是生态学中的一个基本问题。生态学家已经描述了许多原则上能够促进物种共存从而维持生物多样性的机制。大多数这样的共存机制需要或暗示了物种表现不同方面之间的权衡。然而，在多样的自然系统中，简单的功能权衡是否构成共存机制的基础，这一点仍然未知。我们表明，功能权衡解释了索诺兰沙漠一年生冬季植物群落中与低密度恢复（以及共存）相关的长期种群动态中的物种差异。我们开发了一个新的通用框架，通过存储效应来量化共存的程度，并使用这个框架来评估一年生冬季植物群落中存储效应的强度。然后，我们将25年的生命率记录与形态学和生理学测量相结合，以确定生命周期中生长和繁殖阶段促进存储效应共存的物种间功能差异。沿着生长能力和低资源耐受性之间的权衡对物种进行分离，这与多年来物种对环境变化的人口统计学响应差异相对应。生长季节降水是导致物种人口统计学解耦的一个关键环境变量。这些结果表明，促进局部生物多样性的部分解耦的种群动态是如何与物种间资源获取和分配的生理差异相关联的。对于一个相对简单的系统，这些结果展示了长期群落动态与功能生物学之间的联系，这是科学家们长期以来在更复杂系统中所寻求的一种联系。
