三江并流区三种两栖类比较谱系地理学研究

Environmental heterogeneity of the Three Parallel Rivers region is obviously higher than that of other regions of the Hengduan Mountains. Thus, divergence pattern and responses to the Pleistocene climatic oscillations of alpine amphibian species from the Three Parallel Rivers region may differ from that of species from other regions of the Hengduan Mountains, isolation effect of river valleys undercut and mountains uplift on the divergence of alpine amphibians from the Three Parallel Rivers region may be stronger, and historical demography of population may be more stable during climatic oscillations. By investigating the patterns of lineage divergence and historical demographies of Rana shuchinae, Nanorana ventripunctata, and Hyla annectans gongshanensis, this project is going to test for the following four hypotheses: 1) alpine amphibian species from the Three Parallel Rivers region have underwent the process of fragmented divergence and their population structures are strongly consistent with the low-elevational dry hot valleys; 2) alpine amphibian species in the Three Parallel Rivers region retain population stable during the Pleistocene climatic oscillations; 3) genetic difference between populations of alpine amphibian species from the Three Parallel Rivers region is high, and intra-population genetic diversity is low; and 4) vertically genetic divergence between populations at different elevation levels should increase with the increase of elevational difference (Isolation by elevation). By the investigation of these hypotheses, this project will reveal the mechanism of speciation and divergence of alpine amphibian species from the region of Three Parallel Rivers more clearly.

三江并流区的环境异质性明显高于横断山区其它区域。因此，三江并流区高海拔两栖类物种的谱系分化模式、对更新世气候波动的响应以及它们的形成机制可能会不同于横断山区其它区域的两栖类物种，河谷下切与山脉抬升对三江并流区高海拔两栖类物种的隔离效应可能更加强烈，种群历史在气候波动时可能更加稳定。本项目拟通过分析胫腺蛙、腹斑倭蛙和华西雨蛙贡山亚种的遗传变异模式和种群历史来检验以下假设：1)三江并流区高海拔两栖类物种经历片段化分化过程，其遗传结构与低海拔干热河谷强烈对应；2)三江并流区高海拔两栖类物种在更新世气候波动时种群历史保持相对稳定；3)三江并流区高海拔两栖类物种的群体间遗传差异很大，但群体内的遗传多样性很低；4)不同海拔群体间的遗传差异可能会随海拔差异的增加而增加(Isolation By Elevation)。通过对上述假设的检验，本项目将更清晰地揭示三江并流区高海拔两栖类物种的形成与分化机制。

由于高度的环境异质性，滇西北三江并流区的高海拔两栖类物种的遗传结构可能与山脉抬升和河谷下切紧密相关，种群历史在气候波动时可能保持相对稳定。为检验这一假设，我们基于线粒体基因和核基因分析了胫腺蛙和腹斑倭蛙的系统地理结构和种群历史，并对华西雨蛙贡山亚种的系统地理结构做了初步的分析。结果发现，这三个物种的系统地理结构均符合‘东-西隔离’模式。滇西北倭蛙包含两个主要谱系，一支仅分布于金沙江以西，一支仅分布于金沙江以东的中甸高原。胫腺蛙包含三个主要支系，西部支系分布于怒江以西，中部支系分布于金沙江两侧，东部支系则由川西种群组成；其中，中部支系进一步可分成两个亚支，一支由中甸高原上的群体组成，另一支由金沙江以西群体组成。横断山区的贡山雨蛙群体也可分成两个支系，即澜沧江以西支系和澜沧江以东支系。各物种不同种群之间存在明显的遗传分歧。分化时间估算显示，倭蛙和胫腺蛙主要支系的分化都起始于晚中新世，而各支系内部的分化则主要起始于早更新世晚期；贡山雨蛙两个支系的分化发生在中更新世。因此，晚中新世和早更新世晚期以来横断山脉隆升和河谷下切可能是它们的系统地理格局的主要驱动力。种群历史动态分析显示中甸高原面上的倭蛙和胫腺蛙自末次盛冰期以来分别经历了持续的收缩和扩张，而金沙江以西的群体大小总体保持稳定，说明群体对气候波动的响应既与环境异质性的高低有关，也受物种自身特性的影响。上述结果提升了我们对横断山区高海拔两栖类物种多样性形成机制的认识。.此外，系统发育分析显示倭蛙金沙江以西支系与中甸高原支系不形成单系，且Allopaa属嵌套在倭蛙属内，我们认为倭蛙金沙江以西支系应为倭蛙属一隐存种，而Allopaa属则应归入倭蛙属，这一结果提升了我们对倭蛙属分类和多样性的认识。