Asymmetric Distribution of Gene Trees Can Arise under Purifying Selection If Differences in Population Size Exist
Asymmetric Distribution of Gene Trees Can Arise under Purifying Selection If Differences in Population Size Exist
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如果种群大小存在差异，纯化选择下可能会出现基因树的不对称分布
DOI：
10.1093/molbev/msz232
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发表时间：
2020-03-01
影响因子：
10.7
通讯作者：
Zhang, Peng
中科院分区：
文献类型：
--
作者：
He, Chong;Liang, Dan;Zhang, Peng
谱系分类（ILS）是导致基因树不一致的重要因素。对于三种物种的基因树，在中立，兰德和种间基因流动的情况下，ILS产生了基因树的对称分布：与物种树相一致的基因树具有最高的频率，而这两棵不矛盾的树也同样常见。如果违反中性条件，IL的影响可能会改变，从而改变基因树的分布。在这里，我们表明，在纯化的选择下，即使假设突变的适应性在整个物种树中都是恒定的，如果物种之间存在种群差异，基因树的不对称分布将会出现，这与中性下的期望不同。在极端情况下，不一致的树而不是一致的树成为最常见的基因树。此外，我们发现在实际情况下，扫描室相对于灵长类动物和毛刺的位置，基因树分布中的对称性可能会受到纯化选择的强度的影响。在当前的系统发育推论中，研究人员很少考虑纯化选择对基因树分布的影响。这项研究强调了考虑这种影响的必要性。
Incomplete lineage sorting (ILS) is an important factor that causes gene tree discordance. For gene trees of three species, under neutrality, randommating, and the absence of interspecific gene flow, ILS creates a symmetric distribution of gene trees: the gene tree that accords with the species tree has the highest frequency, and the two discordant trees are equally frequent. If the neutral condition is violated, the impact of ILS may change, altering the gene tree distribution. Here, we show that under purifying selection, even assuming that the fitness effect of mutations is constant throughout the species tree, if differences in population size exist among species, asymmetric distributions of gene trees will arise, which is different from the expectation under neutrality. In extremes, one of the discordant trees rather than the concordant tree becomes the most frequent gene tree. In addition, we found that in a real case, the position of Scandentia relative to Primate and Glires, the symmetry in the gene tree distribution can be influenced by the strength of purifying selection. In current phylogenetic inference, the impact of purifying selection on the gene tree distribution is rarely considered by researchers. This study highlights the necessity of considering this impact.