Dance with the Abundant: How Do Rare Tree Species Persist and Contribute to Forest Biodiversity?

除了少数例外，自然界中的大多数物种都是罕见的。稀有物种如何在气候和土地利用的丰富和快速变化的竞争中生存下来一直是科学的一个重大挑战问题。由于人类活动，许多物种的数量正在减少，因此迫切需要了解稀有物种的维护。然而，物种稀有的原因，特别是长寿树种的原因，人们知之甚少。本研究采用创新的方法，从群落生态学的角度研究物种稀有度。在精心设计的全球茎图森林样地网络的基础上，本研究将探讨从热带、亚热带到温带森林的物种稀有度格局及其维持机制。本文将采用野外观测、操作实验和建模等方法，跨空间尺度和系统发育层次研究树种稀有的模式和原因。本研究有四个主要研究组成部分。(1)建立珍稀物种地理分布模型，利用局地发生数据预测全球珍稀物种数量。(2)考察稀有树种的制种和成苗变化，验证物种共存的稀有优势假说。(3)建立分类单元大小分布模型（例如，一个属的大小或一个科的大小），以检验稀有物种是否在系统发育树中随机出现的假设。(4)建立珍稀物种分布与灭绝风险的关系，建立珍稀物种灭绝风险的量化方法。

With few exceptions, the majority of species in nature are rare. How rare species survive competition with the abundant and the rapid changes in climate and land-use has been a major challenging question to science. Given that many species populations are declining in size due to human activities, understanding the maintenance of rare species is urgently needed. However, the causes of species rarity, particularly for long-lived tree species, are poorly known. This study takes innovative approaches to study species rarity from the perspective of community ecology. Built on a well-designed global network of stem-mapped forest plots, this study will investigate the pattern of species rarity and their maintenance mechanisms across latitudinal gradients from tropical, subtropical to temperate forests. Field observation, manipulative experimentation and modeling approaches will be taken to study the patterns and causes of rarity of tree species across spatial scales and phylogenetic hierarchies. This study has four primary research components. (1) Model geographical distribution of rare species for the purpose of predicting global rarity of species from local occurrence data. (2) Investigate the variation in seed production and seedling establishment of rare trees to test the rare species advantage hypothesis for species coexistence. (3) Model the distribution of taxon size (e.g., the size of a genus or the size of a family) to test the hypothesis whether rare species occur randomly across phylogenetic trees. (4) Develop methods for quantifying extinction risk of rare species by establishing relationships between distribution and extinction risk.