Data from: History cleans up messes: the impact of time in driving divergence and introgression in a tropical suture zone

Contact zones provide an excellent arena in which to address questions about how genomic divergence evolves during lineage divergence. They both allow us to infer patterns of genomic divergence in allopatric populations isolated from introgression and to characterize patterns of introgression after lineages meet. Thusly motivated, we analyze genome-wide introgression data from four contact zones in three genera of lizards endemic to the Australian Wet Tropics. These contact zones all formed between morphologically cryptic lineage-pairs within morphologically defined species, and the lineage-pairs meeting in the contact zones diverged anywhere from 3.1 to 5.8 million years ago. By characterizing patterns of molecular divergence across an average of 11K genes and fitting geographic clines to an average of 7.5K variants, we characterize how patterns of genomic differentiation and introgression change through time. Across this range of divergences, we find that genome-wide differentiation increases but becomes no less heterogeneous. On the contrast, we find that introgression heterogeneity decreases dramatically, suggesting that time helps isolated genomes "congeal". Thus, this work emphasizes the pivotal role that history plays in driving lineage divergence.

接触带（contact zones）为探究谱系分化过程中基因组分化的演化机制提供了绝佳的研究平台。其兼具双重研究价值：既可推断无基因渐渗（introgression）隔离的异域种群（allopatric populations）的基因组分化模式，又可刻画谱系相遇后的基因渐渗模式。基于上述研究动机，我们对澳大利亚湿热带特有3个蜥蜴属的4个接触带的全基因组基因渐渗数据展开分析。这些接触带均形成于形态学定义物种内部的形态隐存谱系对之间，且在接触带相遇的谱系对的分化时间介于310万至580万年前。通过对平均1.1万个基因的分子分化模式进行刻画，并对平均7500个变异位点拟合地理梯度（geographic clines），我们解析了基因组分化与基因渐渗模式随时间的变化规律。在这一分化时间区间内，我们发现全基因组分化水平有所提升，但分化的异质性并未降低。与之相反，基因渐渗的异质性显著下降，这表明时间可帮助隔离的基因组“固化”。因此，本研究凸显了历史进程在驱动谱系分化中的关键作用。