中国木本植物多样性中心的物种多样性和遗传多样性关系研究：以领春木群落为例

Hotspots of biodiversity have long been a central focus of ecology and biogeography. Biodiversity is manifested at two fundamental levels: species diversity and genetic diversity. However, species diversity is the most commonly used criterion to identigy biodiversity hotspots, yet genetic diversity is always poorly emphasized. This project aims to identify the hotspots of genetic diversity for woody plant species in China, and to test the concordance in the hotspots of genetic diversity and species diversity. Here, hotspots of genetic diversity are used with reference to regions where most woody plant species show high genetic diversity. First, we will collect papers of case studies concerning the genetic diversity of woody plant species in China, and then synthesize the data to reveal the geographic patterns of genetic diversity. To test the concordance in the hotspots of the two kinds of biodiversity, we also will compare the location of the identified hotspots of genetic diversity with the published hotspots of species diversity. Second, we will choose representative woody plant community and its dominant tree species to test the species-genetic diversity correlation (SGDC) at large scale. If the SGDC in the representative woody plant community is positive, there is a high potential for the concordance in the identified hotspots of genetic diversity and species diversity. We also will study the phylogeography of the dominant tree species to detect the driver (contemporary factors or history events) of the geographic patterns of genetic diversity, and then to reveal the underlying mechanism for the SGDC. Identifying the hotspots of genetic diversity will provide new viewpoint in the field of biodiversity hotspots. Testing the concordance in the hotspots of the two levels of biodiversity is fundamental for at least two reasons: (i) to understand concurrent micro- and macro evolutionary processes, (ii) and to provide a valid framework for conserving not just patterns, but also processes at biogeographical scales.

物种多样性和遗传多样性是生物多样性的两个重要组成部分。然而，长期以来我国生物多样性中心的确定仅考虑物种多样性，并未涉及遗传多样性。那么，我国木本植物是否存在遗传多样性中心？如果存在，它和物种多样性中心是否重叠？本项目拟通过以下两个方面的研究对这两个问题进行探讨。（1）对现有关于我国木本植物遗传多样性的研究进行meta-analysis，揭示遗传多样性的地理分布格局，和已有的物种多样性中心进行比对，探讨遗传多样性中心和物种多样性中心是否重叠；（2）以领春木（Euptelea pleiospermum）和以其为优势种的木本植物群落为研究对象，在物种分布范围尺度上揭示物种多样性和遗传多样性关系，如果二者呈现正相关，则遗传多样性中心在很大程度上会和物种多样性中心重叠。该项目的开展不仅可以为我国生物多样性中心的确定提供新的思路和新的证据，也为保护格局和生物地理学尺度上的过程提供有效的框架。

本项目以领春木（Euptelea pleiospermum）和以其为优势种的木本植物群落为研究对象，揭示物种多样性与遗传多样性的关系，探讨物种多样性与遗传多样性关系的形成原因。主要开展以下几方面的研究：（1）华中-西南生物多样性中心的物种多样性与遗传多样性关系及其驱动因素；（2）分布区尺度上领春木遗传多样性地理格局和遗传结构；（3）纬度和海拔梯度上领春木的种群更新动态：萌蘖和实生苗的权衡；（4）分布区尺度上领春木叶片性状地理格局及其驱动因素。研究结果如下：（1）在中国华中西南地区，在分布区尺度下，以领春木为优势种的珍稀植物群落物种多样性和遗传多样性并未呈现显著的正相关关系。这主要有以下两个因素驱动：①物种多样性和遗传多样性呈现不同的纬度梯度格局；②物种多样性和遗传多样性受不同的环境因子（气候或土壤）影响。（2）遗传多样性和遗传分化的地理格局整体上符合中心-边缘假说。四川盆地而非秦巴山地为遗传障碍。与以往研究结果不同，遗传多样性沿纬度梯度的顶点并未南偏，反而呈现一定程度的北偏；这是由于该物种受冰期后分布区扩张的影响较弱，而其分布区中南部有较大面积不适生境（四川盆地），同时，分布区中北部有较大面积连续适宜生境（秦巴山地）。（3）领春木的相对幼苗密度沿纬度梯度逐渐升高，这为气候变暖条件下领春木向高纬度迁移提供证据。沿不同纬度山地，相对幼苗密度呈现不同的海拔梯度格局，这为海拔梯度上树木更新动态和迁移趋势驱动因素（全球变暖、种间竞争、土地利用变化）的复杂性提供证据。在纬度梯度和海拔梯度上，相对幼苗密度和萌蘖繁殖率均呈现相反的梯度格局，这表明萌蘖繁殖是延缓其分布区“后缘”（trailing edge）收缩的重要策略。（4）局域叶性状变异可以用于推测区域叶变化。在分布区内，叶面积、叶密度、叶片干物质含量、比叶面积和叶片磷含量相对其它指标有较大的变化。叶片性状地理梯度格局，是由于气候作用引起的，温度对叶性状的作用强于降雨。