纬度梯度上领春木的表型可塑性和局域适应性及其驱动因素研究

Understanding alpine plant species’ abilities to cope with climate change is a central question in both conservation biology and global change biology. In long-lived organisms such as tree species, genetic adaptation is slow; and the slow migration rates of most plant species mean that many species will need to face climate change in situ. An important strategy that allows plants to cope with climate change is phenotypic plasticity. The advantage of phenotypic plasticity is that it allows populations to buffer against immediate fitness declines due to rapid climate change, even in the short term, and then it will allow time for evolutionary changes to occur. However, populations that are locally adapted to high elevation environment are expected to be at high risk of extinction. Therefore, understanding the relative importance of phenotypic plasticity and local adaptation is essential for predicting the future fates of mountain plants. In this project, our study species is Euptelea pleiospermum, a tertiary relict tree species endemic to East Asia. First, we will investigate range-wide variation in traits of key life-history stage (e.g. fruit) and associated phenotypic plasticity with environmental conditions (e.g. geography, climate, and soil). Second, fruits of E. pleiospermum will be reciprocally transplanted in common gardens located at low, middle and high latitudes to evaluate phenotypic plasticity and local adaptation of early life stages, which are of particular interest because seed germination and seedling establishment may be crucial life-history stages for survival and persistence in the face of climate change. Last, fruits of E. pleiospermum will be planted in common gardens with different environment conditions (temperature, precipitation, and soil) to explore the drivers of phenotypic plasticity and local adaptation along a latitudinal gradient. In general, this project aims to assess the relative importance of phenotypic plasticity and local adaptation for endemic and rare/endangered tree species in subtropical mountain forests of China to cope with climate change in the future.

山地植物应对气候变化的策略和能力是当前保护生物学和全球变化生物学的研究热点之一。由于向高纬度或海拔迁移和遗传适应均需要一个较长的过程，因此木本植物尤其需要一种能够在原地且较快速的应对气候变化的策略。表型可塑性，作为植物应对短期气候变化的手段，可以在很大程度上帮助植物快速适应气候变化；而局域适应性则很可能限制物种应对气候变化的能力。本项目拟以东亚特有植物领春木（Euptelea pleiospermum）为研究对象，首先在分布区尺度上揭示山地植物自然种群果实性状变异的地理格局，与环境因子进行关联分析，确定其驱动因素（地理、气候、土壤）；然后通过不同纬度间的移栽试验来确定纬度梯度上其表型可塑性和局域适应性；最后通过同质园控制试验（温度、降水、土壤）来确定表型可塑性和局域适应性及其驱动因素。该项目旨在评估表型可塑性和局域适应性在我国亚热带山地珍稀特有木本植物应对气候变化中的作用。

山地植物应对气候变化的策略和能力是保护生物学的研究热点之一。以东亚特有植物领春木为研究对象，通过野外采样和萌发试验来研究种子功能性状地理格局及其驱动因素，并通过同质园试验和交互移栽-控制试验来研究其表型可塑性与局域适应，以及不同种源幼苗生长性状对环境变化的响应。研究内容如下：(1) 分布区尺度上领春木种子性状地理格局及驱动因素; (2) 纬度梯度上领春木表型可塑性与局域适应性; (3) 环境变化下领春木的表型可塑性与局域适应性。. 研究结果：(1) 种子性状在不同种群间存在较大差异，部分性状呈显著的地理格局。年均温和土壤P含量是种子性状变异的主要驱动因子。种子重量和种子N含量对种子萌发率具有显著正效应；母本环境主要通过影响种子形态和养分含量间接影响种子萌发，推测未来气候变暖有可能通过影响种子内在属性而改变种子萌发率。(2) 随种源纬度升高，种子萌发时间T0增长，T50则缩短，分别表现出对高纬度区域春季低温和生长季较短的局域适应。叶片结构性状(面积、周长等)和资源获取性状(SLA和叶密度)未随纬度发生变化，且其野外种群叶片性状的地理格局未能在同质园中保存，表明其具有一定的表型可塑性；而叶片化学计量性状(P含量)呈现出与野外种群一致的经度格局，表现出一定的局域适应性。(3) 幼苗表现(performance)受到种源、移栽样地及其交互作用的显著影响。同一样地不同种源间的比较，以及同一种源不同样地间的比较，均显示出本地优势，即存在局域适应。另外，部分幼苗生长性状受到增温或减雨处理的显著影响。增温使中纬度种源幼苗株高增大，减雨则使叶面积、叶厚度和最长根长增加，叶片N含量减少。地上部生物量、根生物量和全株生物量的表型可塑性高于叶、根性状。中纬度种源的表型可塑性较大，在适应不同环境条件时更具优势。. 本研究揭示了领春木种子性状地理格局、纬度梯度上的表型可塑性和局域适应性，以及幼苗生长对环境变化的响应能力，为预测山地珍稀木本植物如何应对未来气候变化提供了新的科学依据。.