中国石龙子表型的种群间变异：受选择表型的辨析

The general laws and adaptive significance of phenotypic variation in creatures have been the main research field of evolutionary biology. The pattern and magnitude of phenotypic variation are determined by the covariance between genetic and environmental influences across a gradient (e.g., latitude, altitude). Two patterns of phenotypic variation, cogradient versus countergradient variations, identified recently have received increasingly more attention from the scientific community. Cogradient variation occurs when genetic and environmental influences on phenotypic expression are aligned and their joint influence accentuates the change in mean trait value across the gradient, and countergradient variation occurs when genetic and environmental influences on phenotypes oppose one another,thereby diminishing the change in mean trait expression across the environmental gradient. Previous studies in this field have been mostly focused on a limited number of phenotypes, paying little attention to the underlying mechanism that determines phenotypic variation, which should have its own genetic basis and is influenced by the real-time environment. However, the extent to which variation is determined by these two factors has never been well examined. One cannot draw any general conclusions for the patterns observed with a limited number of phenotypes. Thus, more phenotypes should be included. Studies addressing the genetic basis of phenotypic variation are important in uncovering the underlying mechanism for any observed pattern. In this study, we will use the Chinese skink Plestiodon chinensis, a species highly sensitive to the environment, as a model animal to identify the causes for phenotypic variation. We will gather morphological (body size, head size and abdomen size) and physiological (fecundity, egg size, reproductive output, embryonic metabolism and hatchling growth) data from eight geographically separated populations to show the pattern of variation in each examined phenotype. We will determine the relative contributions of phenotypic plasticity and heritability to phenotypic variation by comparing genetic differentiation at microsatellite markers (Fst) with differentiation in phenotypes (Pst, data from the field) and differentiation in quantitative genetic traits (Qst, data from the common garden). Data from this study will allow us to interpret how animals adapt to local environments and how fitness-related traits evolve in nature, and convey information on how animals respond to contrasting selection in heterogeneous environments.

生物表型变异的一般规律和适应意义一直是进化生物学领域的研究热点。近年来生物表型随环境的顺梯度和逆梯度变异模式备受科学界的关注，但已有的研究多局限于个别表型的现象探讨，缺乏变异产生的机制研究。表型变异受遗传和表型可塑性的共同作用，但这两者如何影响表型及其对表型变异的相对贡献仍缺乏深入的探讨，迫切需要进一步研究。本项目将采用表型环境敏感性高的中国石龙子为实验模型，在野外和同园实验条件下收集多个形态和生理表型数据，研究各表型的变异模式。用基于微卫星标记检测种群遗传分化（Fst），将Fst分别与基于野外（Pst）和同园实验下（Qst）表型数据计算的表型分化进行统计对比，辨析受选择的表型以及揭示表型可塑性和遗传性对表型变异的相对贡献。本项目研究结果将有助于阐释动物是如何适应区域环境的、与适合度相关的表型在自然界中是如何进化的，并传达动物在异质性高的环境中如何响应不同选择等信息。

生物表型变异的一般规律和适应意义一直是进化生物学领域的研究热点。近年来生物表型 随环境的顺梯度和逆梯度变异模式备受科学界的关注，但已有的研究多局限于个别表型的 现象探讨，缺乏变异产生的机制研究。表型变异受遗传和表型可塑性的共同作用，但这两 者如何影响表型及其对表型变异的相对贡献仍缺乏深入的探讨，迫切需要进一步研究。本项目采用表型环境敏感性高的中国石龙子为实验模型，收集三个野外和同园实验条件下中国石龙子多个形态，生理和行为等表型数据，研究各表型的变异模式。并用基于线粒体标记检测种群遗传分化（ Fst），与基于野外（Pst）表型数据计算的表型分化进行统计对比，辨析受选择的表型以及揭示表型可塑性和遗传性对表型变异的相对贡献。本项目研究结果得出以下结论：1）来自不同种群的卵孵化期差异显著，且相同孵化温度下幼体大小及形态种群间差异不显著，高纬度种群的幼体各形态表型特征平均值显著大于低纬度种群。2）中国石龙子不同地理种群幼体在个性表型上（胆量大小）存在显著差异，高纬度种群幼体在胆量测试所需时间显著大于低纬度种群；而在新奇实验中，高纬度种群活跃度显著大于低纬度种群；在社会性实验中，高纬度种群活跃度则显著小于低纬度种群；3）研究中各种群FST的均值为0.508，表明各种群间的遗传差异均较大；种群间各PST的均值为0.240，种群间遗传分化值大于对应的表型分化值（FST > PST），说明无论存在遗传漂变与否，种群的形态特征受稳定选择的作用而在异质环境中保持相同或相似，表明遗传均质化作用阻碍了不同种群间的表型分化。本项目所得研究结果有助于阐释动物是如何适应区域环境的、与适合度相关的表型在自然界中是 如何进化的，并传达动物在异质性高的环境中如何响应不同选择等信息。