The ecology and evolution of biodiversity in natural metacommunities

推动群落生态学研究的一个基本目标是了解生物多样性在空间和时间上是如何维持的。在21世纪初，社区生态学被批评为缺乏机械力量，过于偶然。作为回应，现代群落生态学强调两种方法：(1)旨在确定生态过程的机械实验，而不是从描述模式中推断它们；(2)认识到群落通过扩散联系在一起，形成一个区域网络，或“元群落”，为理解生态结果提供了一个一般的预测框架。然而，在实际的自然元群落中，元群落理论的实验测试非常缺乏，因为在野外很难操纵扩散，因此呈现出当今生态学面临的最大知识空白之一。******我的实验室研究的是北加州一年生草地植物元群落的生态学和生物多样性的进化。一年生植物是测试野外元群落过程的理想选择，因为个体和整个群落可以通过种子进行迁移，模拟扩散。在这个系统中，我已经证明了有限的扩散阻止了物种进入合适的栖息地斑块，并且扩散限制表现的空间尺度是由环境结构决定的。然而，我们不知道这一结果随着时间的推移有多稳定，也不知道它在社区/元社区尺度上对多样性的影响。我们将使用可操作的现场实验来测试以下预测，这些预测构成了三个研究目标的基础：******1。如果物种被完美地分类到环境梯度的合适部分（允许测试哪里和为什么会发生不匹配），那么分散会导致物种观察到的占用模式不匹配的模式******2。扩散是非随机的，根据种子传播媒介（如动物、水文）如何连接生境斑块，从一些斑块定向地发生到另一些斑块，影响群落丰富度和组成******3。由于扩散导致种间竞争者在一些生境斑块上重叠，而不是在其他生境斑块上重叠，因此扩散历史指导了竞争相互作用和持久性的进化******提出的目标弥合了元群落生态学，进化生态学和景观生态学之间的基本差距，测试了元群落预测的现实可行性，推进了基础理论。基础理论可以为保护行动提供信息（例如，应该在多大的空间尺度上管理景观以保护区域过程？），无论是在我的研究系统中，还是在其他地方，如加拿大森林，生态动态观察较慢（例如，长世代时间）或多样性不易操纵的地方。最后，我们将提供新的证据，证明生态过程如何以及为什么在自然系统中跨尺度相互作用，推动进化和生物多样性的尺度依赖性。

***A fundamental goal motivating community ecology research is to understand how biodiversity is maintained in space and time. In the early 2000s, community ecology was criticized as lacking mechanistic power and being too wrought with contingency. In response, modern community ecology emphasizes two approaches: (1) mechanistic experiments designed to pinpoint ecological processes, rather than infer them from descriptive patterns, and (2) recognizing that communities are linked by dispersal to form a regional network, or “metacommunity”, offering a general predictive framework to understand ecological outcomes. However, experimental tests of metacommunity theory in actual natural metacommunities are exceptionally scarce given the difficulty of manipulating dispersal in the field, thus presenting one of the greatest knowledge gaps facing ecology today.******My lab studies the ecology and evolution of biodiversity in a metacommunity of annual grassland plants in Northern California. Annual plants are ideal to test metacommunity processes in the field given that individuals and whole communities can be translocated via seed, simulating dispersal. In this system, I have shown that limited dispersal prevents species from accessing suitable habitat patches, and that the spatial scales at which dispersal limitation manifests is determined by environmental structure. However, we do not know how stable this outcome is through time or its consequences for diversity at community/metacommunity scales. We will use manipulative field experiments to test the following predictions that form the basis of three research objectives:******1. Dispersal causes species' observed occupancy patterns to mismatch patterns that would be expected if species were perfectly sorted into suitable portions of environmental gradients (allowing tests of where and why mismatches occur)******2. Dispersal is non-random, occurring directionally from some patches to others based on how seed dispersal vectors (e.g., animals, hydrology) connect habitat patches, affecting community richness and composition******3. Because dispersal causes interspecific competitors to overlap in some habitat patches and not others, dispersal histories direct the evolution of competitive interactions and persistence******The proposed objectives bridge fundamental gaps between metacommunity ecology, evolutionary ecology, and landscape ecology, testing the real-world feasibility of metacommunity predictions, advancing basic theory. Basic theory can then inform conservation action (e.g., at what spatial scale should landscapes be managed to preserve regional processes?), both in my study system and in others, such as Canadian forests, where ecological dynamics are slower to observe (e.g., long generation times) or diversity less amenable to manipulation. Ultimately, we will provide novel evidence of how and why ecological processes interact across scales in natural systems, driving evolution and the scale-dependence of biodiversity.