A multispecies coalescent model for quantitative traits

We present a multispecies coalescent model for quantitative traits that allows for evolutionary inferences at micro- and macroevolutionary scales. A major advantage of this model is its ability to incorporate genealogical discordance underlying a quantitative trait. We show that discordance causes a decrease in the expected trait covariance between more closely related species relative to more distantly related species. If unaccounted for, this outcome can lead to an overestimation of a trait's evolutionary rate, to a decrease in its phylogenetic signal, and to errors when examining shifts in mean trait values. The number of loci controlling a quantitative trait appears to be irrelevant to all trends reported, and discordance also affected discrete, threshold traits. Our model and analyses point to the conditions under which different methods should fare better or worse, in addition to indicating current and future approaches that can mitigate the effects of discordance.

本研究提出一种面向数量性状（quantitative traits）的多物种溯祖模型（multispecies coalescent model），可支持微观进化与宏观进化尺度下的进化推断。该模型的核心优势之一，在于能够整合数量性状背后的基因系谱冲突（genealogical discordance）。本研究证实，相较于亲缘关系较远的物种，基因系谱冲突会降低亲缘关系较近物种间的期望性状协方差。若未对该效应加以校正，则会引发一系列问题：高估性状的进化速率、削弱其系统发育信号（phylogenetic signal）强度，以及在检测性状均值演化偏移时引入误差。控制数量性状的基因座（loci）数量与本研究报道的所有趋势均无关联，且基因系谱冲突同样会对离散阈值性状（discrete, threshold traits）产生影响。本研究提出的模型与分析不仅明确了不同方法优劣表现的适用条件，同时也指明了可缓解基因系谱冲突负面影响的现有与未来研究路径。