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稀有物种。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，一直是科学面临的一个重大挑战问题。鉴于由于人类活动，许多物种种群的数量正在减少，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，人们知之甚少。本研究从群落生态学的角度对物种稀有性进行了创新性的研究。这项研究建立在一个设计良好的树干测绘森林地块的全球网络基础上，将调查从热带、亚热带到温带森林的纬度梯度上物种稀有的模式及其维持机制。将采取实地观察、操作实验和建模的方法，研究稀有树种在空间尺度和系统发育等级上的格局和原因。这项研究由四个主要研究部分组成。(1)建立稀有物种地理分布模型，以便从局部发生数据预测全球稀有物种。(2)调查珍稀树种在种子生产和成苗过程中的变异，以验证物种共存的稀有树种优势假说。(3)模拟分类单元大小的分布(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上随机出现的假设。(4)通过建立分布与灭绝风险之间的关系，发展稀有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.