Li Yi-Shao, Chang Chung-Te, Wang Chun-Neng, Thomas Philip, Chung Jeng-Der, Hwang Shih-Ying
Department of Life Science, National Taiwan Normal University, Taipei, Taiwan.
Department of Geography, National Taiwan University, Taipei, Taiwan.
Front Plant Sci. 2018 Aug 8;9:1148. doi: 10.3389/fpls.2018.01148. eCollection 2018.
The question of what determines divergence both between and within species has been the central topic in evolutionary biology. Neutral drift and environmentally dependent divergence are predicted to play roles in driving population and lineage divergence. However, neutral drift may preclude adaptation if the rate of gene flow between populations is high. Here, we sampled populations of three Taiwania () lineages occurring in Taiwan, the mainland of China (Yunnan-Myanmar border), and northern Vietnam, and tested the relative strength of neutral drift and divergent selection in shaping divergence of those populations and lineages. We quantified genetic and epigenetic variation, respectively, using amplified fragment length polymorphism (AFLP) and methylation-sensitive amplification polymorphism (MSAP). Analysis of 1413 AFLP and 462 MSAP loci using frequency-based genome scan methods and generalized linear models (GLMs) found no potential selective outliers when only Taiwanese populations were examined, suggesting that neutral drift was the predominant evolutionary process driving differentiation between those populations. However, environmentally associated divergence was found when lineages were compared. Thirty-two potential selective outliers were identified based on genome scans and their associations with environmental variables were tested with GLMs, generalized linear mixed effect models (GLMMs), and model selection with a model averaging approach. Ten loci (six AFLP and four MSAP) were found to be strongly associated with environmental variables, particularly monthly temperature variation and normalized difference vegetation index (NDVI) using model selection and a model averaging approach. Because only a small portion of genetic and epigenetic loci were found to be potential selective outliers, neutral evolutionary process might also have played crucial roles in driving lineage divergence, particularly between geographically and genetically isolated island and mainland Asia lineages. Nevertheless, the vast amount of neutral drift causing genetic and epigenetic variations might have the potential for adaptation to future climate changes. These could be important for the survival of Taiwania in different geographic areas.
是什么决定了物种间和物种内的分化，这一问题一直是进化生物学的核心主题。中性漂变和环境依赖型分化预计在推动种群和谱系分化中发挥作用。然而，如果种群间的基因流动速率很高，中性漂变可能会妨碍适应性。在这里，我们对分布在台湾、中国大陆（云南 - 缅甸边境）和越南北部的三个台湾杉谱系的种群进行了采样，并测试了中性漂变和分化选择在塑造这些种群和谱系分化中的相对强度。我们分别使用扩增片段长度多态性（AFLP）和甲基化敏感扩增多态性（MSAP）来量化遗传和表观遗传变异。使用基于频率的基因组扫描方法和广义线性模型（GLM）对1413个AFLP位点和462个MSAP位点进行分析，结果发现，仅检查台湾种群时未发现潜在的选择异常值，这表明中性漂变是推动这些种群间分化的主要进化过程。然而，在比较谱系时发现了与环境相关的分化。基于基因组扫描鉴定出了三十二个潜在的选择异常值，并使用GLM、广义线性混合效应模型（GLMM）以及采用模型平均方法的模型选择来测试它们与环境变量的关联。通过模型选择和模型平均方法发现，有十个位点（六个AFLP和四个MSAP）与环境变量密切相关，特别是月温度变化和归一化植被指数（NDVI）。由于仅发现一小部分遗传和表观遗传位点是潜在的选择异常值，中性进化过程可能在推动谱系分化中也发挥了关键作用，特别是在地理和遗传上隔离的岛屿和亚洲大陆谱系之间。尽管如此，导致遗传和表观遗传变异的大量中性漂变可能具有适应未来气候变化的潜力。这对于台湾杉在不同地理区域的生存可能很重要。
