横断山区华西蟾蜍的配对模式及其地理变异

More and more scientists study evolution of mating patterns in species since Darwin (1871) propose sexual selection theory. Mating pattern is defined as the types of the members of one sex choosing actively individuals of the opposite sex, or competition between members of the same sex for access to individuals of the opposite sex in a breeding aggregation in a species at a given time. Differential mating success of individuals during a single breeding season can contribute to variation in lifetime reproductive success, and this differential success is reflected in population patterns of mating. Mating pattern may result from competition for mates or mate choice, the two proximate components of sexual selection. Competition among individuls of one sex for individuals of the opposite sex and selection of one sex by the opposite sex, may lead to a size-dependent or to a size-assortative mating pattern. Mating pattern affects evolution and ecology of species which benefits to breeding behaviour and speciation in nature. Therefore, mating pattern of species is of central importance to evolutionary biology. Previous results from our studies have been shown that mating patterns of the Andrew's toad, Bufo andrewsi, a species widely distributed in the Hengduan mountains, western China, exhibits elevational variations among populations and some of this variation can be explained by population density, the operational sex ratio and the length of breeding season affected by environmental factors (i.e. temperature and rainfall). Therefore, we provide a hypothesis that there is a geographic variations in mating patterns of B. andrewsi populations and population density, the operational sex ratio and the length of breeding season can explain the mating patterns variations. In order to test this hypothesis, we plan to study geographic variations in mating patterns of B. andrewsi using controlling experiments，behaviour observation and genetic analysis in four National Nature Reserves with different latitude and elevation populations in the Hengduan mountains in western China. Our aims are: (1) to test whether geographic variations in mating patterns occur in B. andrewsi populations; (2) how do vary mating patterns in B. andrewsi among populations we plan to study; (3) what are the proximate factors affecting geographic variations in mating patterns in B. andrewsi. According to results of testing this hypothesis, we will gain insight into the molecular mechanism of geographic variations in mating patterns in B. andrewsi in the Hengduan mountains.

配对模式是指生物种群内雌雄个体相互选择最佳配偶的方式，它能够对性选择等重要的生态和进化过程产生深远的影响，从而导致不同地理种群间产生形态分化，甚至导致新物种的形成，故配对模式的研究虽已有100多年的历史，至今仍是动物进化生物学研究中最富有活力的领域。我们前期研究发现，华西蟾蜍的配对模式存在海拔变异，且变异与种群密度、操作性比和繁殖季节性有关。为此，我们假设：华西蟾蜍配对模式存在地理变异，且种群密度、操作性比和繁殖季节性是导致其地理变异的主要因素。为检验该假设，本项目拟以横断山区华西蟾蜍四个自然保护区不同地理种群为研究对象，采用控制实验、标记重捕和遗传分析的方法，比较研究华西蟾蜍：（1）是否存在配对模式的地理变异？（2）如果存在，那么不同地理种群配对模式怎样发生变化？以及（3）影响配对模式地理变异的因素有哪些？通过对华西蟾蜍配对模式理论假设的验证，揭示华西蟾蜍配对模式地理变异分子机制。

配对模式是指生物种群内雌雄个体相互选择最佳配偶的方式，它能够对性选择等重要的生态和进化过程产生深远的影响，从而导致不同地理种群间产生形态分化，甚至导致新物种的形成，故配对模式的研究虽已有100多年的历史，至今仍是动物进化生物学研究中最富有活力的领域。我们于2015年1月至2018年12月以横断山区华西蟾蜍四个自然保护区不同地理种群为研究对象，采用控制实验、标记重捕和遗传分析的方法对华西蟾蜍的配对模式地理变异进行了系统研究，并验证了华西蟾蜍配对模式存在地理变异，且种群密度、操作性比和繁殖季节性是导致其地理变异的主要因素的理论假设。结果发现：华西蟾蜍配对模式存在海拔变异，由于高海拔种群有更低的密度，更小的性比和更短的繁殖季节长度，因此高海拔种群表现出更随机的配对方式，低海拔种群由于竞争更加强烈，所以表现为更为明显的大小匹配；同时，华西蟾蜍两性大小异性随环境的种群密度和竞争压力改变而改变，两性大小异性程度随雌体身体增加而增加，与伦斯法则相反，最后我们发现华西蟾蜍配对模式和配对体的亲缘关系随环境的种群密度和控制性比密切相关，低密度和性比的种群的配对个体间有更近的亲缘关系。因此，华西蟾蜍不同地理种群配对模式存在明显的地理变异，其配对模式的地理变异与密度、控制性比和繁殖季节长度有关，研究发现与理论假设一致。相应的科研成果在Molecular Ecology, Evolution, Oecologia, Frontiers in Zoology等刊物上发表。