Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, CO 80303, USA.
Proc Biol Sci. 2012 Dec 22;279(1749):5058-65. doi: 10.1098/rspb.2012.0813. Epub 2012 Jun 13.
Diverse geographical modes and mechanisms of speciation are known, and individual speciation genes have now been identified. Despite this progress, genome-wide outcomes of different evolutionary processes during speciation are less understood. Here, we integrate ecological and spatial information, mating trials, transplantation data and analysis of 86 130 single nucleotide polymorphisms (SNPs) in eight populations (28 pairwise comparisons) of Timema cristinae stick insects to test the effects of different factors on genomic divergence in a system undergoing ecological speciation. We find patterns consistent with effects of numerous factors, including geographical distance, gene flow, divergence in host plant use and climate, and selection against maladaptive hybridization (i.e. reinforcement). For example, the number of highly differentiated 'outlier loci', allele-frequency clines and the overall distribution of genomic differentiation were recognizably affected by these factors. Although host use has strong effects on phenotypic divergence and reproductive isolation, its effects on genomic divergence were subtler and other factors had pronounced effects. The results demonstrate how genomic data can provide new insights into speciation and how genomic divergence can be complex, yet predictable. Future work could adopt experimental, mapping and functional approaches to directly test which genetic regions are affected by selection and determine their physical location in the genome.
已知物种形成有多种地理模式和机制，并且现在已经确定了个别物种形成基因。尽管取得了这一进展，但物种形成过程中不同进化过程的全基因组结果仍了解较少。在这里，我们整合了生态和空间信息、交配试验、移植数据以及对 86130 个单核苷酸多态性（SNP）的分析，对 Timema cristinae 竹节虫的 8 个种群（28 对比较）进行了分析，以检验不同因素对正在经历生态物种形成的系统中基因组分化的影响。我们发现的模式与多种因素的影响一致，包括地理距离、基因流、寄主植物使用和气候的分化以及对不良杂交（即强化）的选择。例如，高度分化的“异常基因座”、等位基因频率渐变和基因组分化的总体分布数量明显受到这些因素的影响。尽管寄主的使用对表型分化和生殖隔离有很强的影响，但它对基因组分化的影响较为微妙，其他因素的影响更为显著。这些结果表明基因组数据如何为物种形成提供新的见解，以及基因组分化如何变得复杂但可预测。未来的工作可以采用实验、图谱和功能方法，直接测试哪些遗传区域受到选择的影响，并确定它们在基因组中的物理位置。
