Data from: Fruit evolution and diversification in campanulid angiosperms

With increases in both the size and scope of phylogenetic trees, we are afforded a renewed opportunity to address long standing comparative questions, such as whether particular fruit characters account for much of the variation in diversity among flowering plant clades. Studies to date have reported conflicting results, largely as a consequence of taxonomic scale and a reliance on potentially conservative statistical measures. Here we examine a larger and older angiosperm clade, the Campanulidae, and infer the rates of character transitions among the major fruit types, emphasizing the evolution of the achene fruits that are most frequently observed within the group. Our analyses imply that campanulids likely originated bearing capsules, and that all subsequent fruit diversity was derived from various modifications of this dry fruit type. We also found that the preponderance of lineages bearing achenes is a consequence of not only being a fruit type that is somewhat irreversible once it evolves, but one that also seems to have a positive association with diversification rates. While these results imply the achene fruit type is a significant correlate of diversity patterns observed across campanulids, we conclude that it remains difficult to confidently and directly view this character state as the actual cause of increased diversification rates.

随着系统发育树（phylogenetic trees）的规模与覆盖范围持续扩张，我们获得了全新契机以解答长期悬而未决的比较生物学问题——例如特定的果实性状是否极大程度上解释了显花植物支系间的多样性差异。截至目前的相关研究已得出相互矛盾的结论，这在很大程度上源于分类学尺度的差异，以及对潜在偏保守的统计方法的依赖。本研究聚焦于一个体量更大、演化历史更久远的被子植物支系（angiosperm clade）——桔梗亚纲（Campanulidae），推断了主要果实类型间的性状转换速率，并着重探讨了该类群中最为常见的瘦果（achene）的演化历程。我们的分析结果显示，桔梗亚纲类群的祖先类群大概率以蒴果（capsule）为果实类型，后续所有的果实多样性均由这一干燥果实类型的多种演化修饰所产生。我们还发现，拥有瘦果的支系占据多数这一现象，不仅是因为该果实类型一旦演化便具有一定的不可逆转性，还因为其似乎与物种多样化速率呈显著正相关关系。尽管上述结果表明，瘦果这一果实类型与桔梗亚纲类群中观察到的多样性模式存在显著关联，但我们仍认为，难以确凿且直接地将该性状状态视为物种多样化速率提升的真正诱因。