Data from: Non-equilibrium dynamics and floral trait interactions shape extant angiosperm diversity

Why are some traits and trait combinations exceptionally common across the tree of life, whereas others are vanishingly rare? The distribution of trait diversity across a clade at any time depends on the ancestral state of the clade, the rate at which new phenotypes evolve, the differences in speciation and extinction rates across lineages, and whether an equilibrium has been reached. Here we examine the role of transition rates, differential diversification (speciation minus extinction), and non-equilibrium dynamics on the evolutionary history of angiosperms, a clade well known for the abundance of some trait combinations and the rarity of others. Our analysis reveals that three character states (corolla present, bilateral symmetry, reduced stamen number) act synergistically as a key innovation, doubling diversification rates for lineages in which this combination occurs. However, this combination is currently less common than predicted at equilibrium because the individual characters evolve infrequently. Simulations suggest that angiosperms will remain far from the equilibrium frequencies of character states well into the future. Such non-equilibrium dynamics may be common when major innovations evolve rarely, allowing lineages with ancestral forms to persist, and even outnumber those with diversification-enhancing states, for tens of millions of years.

为何部分性状及其组合在生命之树中极为常见，而另一些却罕至绝迹？任意时期内，单系群（clade）内的性状多样性分布，取决于该单系群的祖先状态、新表型的演化速率、不同支系间物种形成与灭绝速率的差异，以及是否达到演化平衡。本文探讨了性状转换速率、差异化分化（物种形成速率减灭绝速率）以及非平衡动态在被子植物（angiosperms）演化历史中的作用——该类群以部分性状组合丰富、另一些性状组合稀缺而著称。我们的分析显示，三种性状状态（具花冠（corolla）、两侧对称（bilateral symmetry）、雄蕊数目减少）作为关键创新（key innovation）协同发挥作用，使携带该组合的支系的分化速率提升一倍。然而，由于各单个性状的演化频率极低，当前该性状组合的出现频率仍低于平衡状态下的预测值。模拟实验表明，被子植物在未来相当长的时间内仍将显著偏离各性状状态的平衡频率。当重大创新的演化频率极低时，这类非平衡动态可能较为普遍：携带祖先形态的支系可存续数千万年，其数量甚至超过携带提升分化速率性状的支系。