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，一直是科学界面临的一个重大挑战。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，物种稀少的原因，特别是长寿树种，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。建立在一个精心设计的干映射森林地块的全球网络，这项研究将调查物种稀有性的模式和它们的维护机制，跨越纬度梯度从热带，亚热带到温带森林。将采取实地观察、人工实验和建模方法，研究不同空间尺度和系统发育层次的树种稀有模式和原因。这项研究有四个主要的研究组成部分。(1)模拟稀有物种的地理分布，以根据当地发生数据预测物种的全球稀有度。(2)调查珍稀树种种子生产和成苗的变异，以检验物种共存的珍稀物种优势假说。(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）来检验稀有物种是否在系统发育树中随机出现的假设。(4)通过建立分布和灭绝风险之间的关系，开发量化稀有物种灭绝风险的方法。该研究具有重要的理论意义和应用价值。从这项研究中开发的概念，模型和方法将大大提高我们的能力，以了解稀有物种对生物多样性的贡献，预测气候和土地利用变化对生物多样性丧失的影响，并更好地保护和管理生物多样性在世界上，以及在加拿大。

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. This study is significant in both theory and application. The concepts, models and methods developed from this study will greatly enhance our ability to understand the contribution of rare species to biodiversity, to predict the impact of climate and land-use change on loss of biodiversity, and to better conserve and manage biodiversity in the world as well as in Canada.