Fig_S7

FIGURE S7. Illustration of an example case of ancient population subdivision that could lead to an identical data signal as that created by genetic introgression between mosaic birds and Z. chrysops. Note that substantial levels of persistent ancestral subdivision (across speciation events) are needed to account for such patterns of asymmetry of tree signal (Slatkin and Pollard 2008). Given most Andean birds’ turbulent Pleistocene evolutionary history, this alternative scenario is probably unlikely.图S7：一例古代种群分化的示意案例，该场景可产生与镶嵌型鸟类与Z. chrysops之间基因渐渗所诱导的完全一致的数据信号。需指出，要解释此类系统发育信号不对称的模式，必须存在持续程度较高的祖先种群分化（跨越物种形成事件）（Slatkin与Pollard，2008）。鉴于多数安第斯鸟类在更新世时期动荡多变的演化历史，这一替代假说大概率不成立。