Geographical variation in community divergence: insights from tropical forest monodominance by ectomycorrhizal trees

Convergence occurs in both species traits and community structure, but how convergence at the two scales influences each other remains unclear. To address this question, we focus on tropical forest monodominance, in which a single, often ectomycorrhizal (EM) tree species occasionally dominates forest stands within a landscape otherwise characterized by diverse communities of arbuscular mycorrhizal (AM) trees. Such monodominance is a striking potential example of community divergence resulting in alternative stable states. However, it is observed only in some tropical regions. A diverse suite of AM and EM trees locally codominate forest stands elsewhere. We develop a hypothesis to explain this geographical difference using a simulation model of plant community assembly. Simulation results suggest that in a region with a few EM species (e.g., South America), EM trees experience strong selection for convergent traits that match the abiotic conditions of the environment. Consequently, EM sp...

物种性状与群落结构均存在趋同现象，但这两个尺度上的趋同如何相互影响仍不明确。为解答该科学问题，我们聚焦热带森林单优群落现象：在原本以丛枝菌根（arbuscular mycorrhizal, AM）树木多样群落为特征的景观中，偶尔会有单一（通常为外生菌根（ectomycorrhizal, EM））树种主导局部林分。这类单优群落是引发替代稳定态形成的群落分化的典型潜在案例，但该现象仅在部分热带区域被观测到；在其他区域，多种丛枝菌根与外生菌根树木会在林分中局部共优。我们通过植物群落构建模拟模型提出了一套解释该地理分布差异的假说。模拟结果显示，在外生菌根树种较少的区域（如南美洲），外生菌根树木会受到强烈的选择作用，演化出适配环境非生物条件的趋同性状。由此，外生菌根树种的……