第四纪冷暖交替对我国5种南方山地蛙类分布的影响

The Pleistocene climatic oscillations have notable effects on the geographic distribution of organisms. Generally, glacial cold climate causes the distribution of a species contracting to lower latitude, while interglacial warm climate causes it expanding to higher latitude. However, evidences mainly from North America and high latitude regions of Eurasia suggested that the distribution of cold-adapted species expanded in the glacial period and contracted during the interglacial period. Cold-adapted species can be found in both high latitude and high altitude regions. In this project, we introduce this topic into relatively low latitude mountain regions of eastern Eurasia and focus on the subtropical mountain region of moderate heights in southern China. Five frog species from four families are selected as an example to explore the effect of the glacial-interglacial cycles on the distribution of species adapting to cold environments in relatively high altitudes of the mountain region. These five species exhibit three distribution patterns, which will facilitate both interspecific and intraspecific comparisons. As the first pattern, for Xenophrys kuatunensis and Hyla sanchiangensis, populations are isolated in relatively high altitudes of the mountain region. Secondly, for Amolops chunganensis and Rhacophorus chenfui, populations are isolated in high altitudes of this region, while in continuous high altitudes around the Sichuan Basin, populations can be found to be continuous in a wide range. Last, as Hylarana latouchii adapted various environments between low and high altitudes, it exhibits a continuous pattern of distribution in the subtropical region. For each species, alternative working hypotheses are proposed for testing. For instance, distribution range can be hypothesized to expand in glacial periods and contract during interglacial periods, or vice versa, or climatic oscillations can be hypothesized to have no significant effects on the distribution. Based on mitochondrial DNA and STR data, various population genetic and phylogeographic approaches can be employed to examine predictions of these hypotheses. The results of this project will provide new insights toward a better understanding of the influences of glacial-interglacial cycles on organisms.

第四纪冷暖交替对生物分布的影响主要表现为物种的分布区在冰期向低纬度退缩、于间冰期向高纬度扩张。作为重要的反例，主要来自欧亚大陆中高纬度和北美的证据提示，适应高纬或高海拔寒冷环境物种的分布可在冰期扩张、间冰期收缩。我们将该主题引入欧亚大陆东部的中低纬山地系统，将我国亚热带中低山地作为目标区域，以来自4个科的5种蛙类为例，基于线粒体DNA和微卫星数据，主要运用种群遗传学的研究手段，通过检验一系列相互竞争的工作假说，对适应该区域较高海拔相对寒冷环境的物种如何在分布上相应冷暖交替这一问题进行探讨。研究对象中，挂墩角蟾和三港雨蛙间断分布于该区域较高海拔；崇安湍蛙和经甫树蛙不仅高海拔间断分布于该区域，也在四川盆地周边连续高海拔区域有较大范围连续分布；阔泽蛙适应该区域不同海拔环境、呈连续分布。这3种分布型利于种内、种间的对比和类比。本项目的开展将为全面认识生物如何在分布上响应第四纪冷暖交替提供新的信息。

第四纪冷暖交替对生物分布的影响主要表现为物种的分布区在冰期向低纬度退缩、于间冰期向高纬度扩张。而主要来自欧亚大陆中高纬度和北美的证据提示，适应高纬或高海拔寒冷环境物种的分布可在冰期扩张、间冰期收缩。我们将该主题引入欧亚大陆东部的中低纬山地系统，在华南亚热带中低山地中，以来自4个科的5种蛙类为例，基于DNA序列、微卫星、SNP数据，运用种群遗传和谱系地理研究手段，通过检验7个相互竞争的工作假说，对适应该区域较高海拔相对寒冷环境的物种如何在分布上响应冷暖交替这一问题进行探讨。研究对象中，三港雨蛙和福建掌突蟾间断分布于该区域较高海拔；崇安湍蛙和经甫树蛙不仅高海拔间断分布于该区域，也在四川盆地周边连续高海拔区域有较大范围连续分布；阔泽蛙适应该区域不同海拔环境、呈连续分布。分析方法包括基因树，单倍型网络，分子钟分析，祖先分布区重建，种群内遗传多样性，种群间分化程度，PCoA，AMOVA，IBD，微卫星聚类，种群基因流，以及各种种群大小历史动态分析如EBSP和相似贝叶斯。所得结果支持在华南亚热带中低山地内，作为间断分布于较高海拔相对寒冷环境蛙类的代表，三港雨蛙、福建掌突蟾、崇安湍蛙、经甫树蛙在分布上表现为冰期扩张、间冰期收缩；同一区域高低海拔连续分布的阔褶蛙受冷暖交替的影响不大，种群大小无普遍的近期变化；在四川盆地周边的连续高海拔区域连续分布的崇安湍蛙和经甫树蛙种群受冷暖交替的影响不大。我们工作支持东亚亚热带山地于间冰期为冷适应物种提供高海拔避难所，在种下水平展示了地形拓扑结构对物种响应气候变化的影响，为更全面认识第四纪冷暖交替对生物分布、多样性格局形成的影响提供了新的信息。