青海沙蜥种组蜥蜴对局域环境的生态适应：进化与表型可塑性响应

Uncovering the underlying mechanism for ecological adaptation of organisms to local environments is a central goal of evolutionary biology. Species or populations inhabiting environmentally heterogeneous regions provide an excellent opportunity in this respect. The selective forces imposed by local environments and phenotypes under selection have been studied in a wide range of vertebrate taxa, but not including any lizard species. Here, we use lizards of three species within the Phrynocephalus vlangalii species complex endemic to China as model animals to address four questions: (1) Are fitness-related phenotypes phylogenetically independent, thus varying more tightly with species’ distribution and local environment? (2) Is genetic diversity of a population determined by habitat suitability? (3) Does a given phenotype have an unique pattern of geographic variation, thus having an unique position in the continuum of cogradient-countergradient variation? (4) Is the critical rate of environmental change for a phenotype correlated with both habitat speciality and habitat suitability? We will conduct a series of common garden experiments to collect data on 18 morphological, physiological and life-history variables (phenotypes) and then calculate Qst for each phenotype. We will use 9 microsatellite, 3 nDNA (RAG1、PRLR and PDC) and 3 mtDNA (Cyt b、ND4 and COI) marks to resolve phylogenetic relationships among species within the complex and intra-specific units, and to calculate Fst. We will contrast Qst with Fst to show whether a phenotype is selected and thus locally adapted. We will use phylogenetic ANOVA, phylogenetic ANCOVA or phylogenetic generalized least squares to determine associations of currently observed patterns of phenotypic variation with species' distribution and local environment. We will use genetic information provided by different types of molecular marks to examine the relationship between population genetic diversity and habitat suitability, and the effect of population evolution duration on population genetic diversity. Hypotheses to be tested in this study include: (1) phenotypes should be similar among species and lineages of the same species if they are phylogenetically independent and tightly correlated with local environment; (2) population genetic diversity should be higher in the region where habitat suitability if it varies geographically; (3) phenotypes should have unique positions in the continuum of cogradient-countergradient variation if their evolutionary and plastic responses to selection differ from each other; and (4) the critical rate of environmental change for a phenotype should be slower in species with a smaller rage it the rate is correlated with both habitat speciality and habitat suitability. Data generated from this study will allow us to better understand how lizards of the Phrynocephalus vlangalii species complex adapt to local environments and, more importantly, they might provide insight into the evolutionary divergence of viviparous Phrynocephalus species as the consequence of environmental change associated with uplift of the Qinghai-Tibet Plateau.

探讨生物对局域环境生态适应的潜在机制是进化生物学的核心任务之一。申请人拟用我国特有的青海沙蜥种组三种蜥蜴，通过假设检验的研究方法探讨4个问题：（1）适合度相关的表型是否因具有谱系独立性而更多地与物种的地理分布和局域环境条件有关？（2）野外种群遗传多样性是否与栖息地适合性有关？（3）特定表型是否因具有独有的环境变异模式而在逆梯度顺梯度变异连续谱占据独有的位点？（4）表型临界环境变化速率是否与栖息地特异性和适合性有关？申请人拟用同园实验收集18个表型数据，计算Qst，用每种9个微卫星标记以及其它核和线粒体标记计算Fst，通过对比Qst与Fst判定表型是否受选择并与局域适应有关。申请人将基于谱系ANOVA、谱系ANCOVA和PGLS揭示表型与地理分布和局域环境之间的关联性，并利用上述提供不同遗传多样性信息的分子标记分析种群遗传多样性与栖息地适合性之间的关系，推测种群进化时长对遗传多样性的影响。

揭示生物对局域环境的适应机制是进化生物学领域的中心研究课题。生活于异质性环境中的物种为开展此方面的研究提供了绝好的机会。局域环境的选择力和受选择性状方面的研究已涉及跨度较大的脊椎动物类群，但不包括沙蜥属（Phrynocephalus）蜥蜴。因此，本项目以青海沙蜥种组3种卵胎生蜥蜴为材料检验如下4个与进化和表型可塑性响应有关的假设：1）若表型具有谱系独立性而更多地与局域环境条件有关，则不同物种或同种不同支系种群的个体在相似的环境中应具有相似的表型；2）若种群遗传多样性存在地理变异，则栖息地适合性较高的区域应具有较高的种群遗传多样性；3）若不同表型对选择的进化和可塑性响应存在差异，则各表型应具有各自独有的环境变异模式；4）表型临界环境变化速率与栖息地特异性和适合性有关，则分布区较小的物种应具有小于广布种的速率测定值。为检验这些假设，开展一系列同园实验收集用于计算有关形态、生理和生活史的Qst值所需的数据，用微卫星、核基因和线粒体基因等中性标记计算辨析种内和种间谱系关系并计算Fst值，通过比较Qst和Fst辨析被检表型是否受选择；用谱系ANOVA、ANCOVA或广义最小二乘法研究观察到的表型变异格局与物种分布和局域环境之间的关联性；用获得的遗传信息检测遗传多样性与生境适应性之间的关系，以及种群进化时长多遗传多样性的影响。本项研究获得如下主要结果：1）若干表型具有谱系依赖性并随局域环境变化；2）种群遗传多样性有地理变异，在生境适宜性较高的区域遗传多样性较高；3）各表型在顺梯度-逆梯度变异连续谱上有各自的位置，其对选择的进化和可塑性相应各不相同；4）表型临界环境变化速率与生境适应性和特异性有关，分布区较小的物种速率较低。本研究首次报道了局域适应驱动青海沙蜥种组的物种分化，更重要的是，证明了卵胎生沙蜥物种分化是青藏高原隆起后环境变化的结果。