Data from: Temperate radiations and dying embers of a tropical past: the diversification of Viburnum

We used a near-complete phylogeny for the angiosperm clade Viburnum to assess lineage diversification rates, and to examine possible morphological and ecological factors driving radiations. Maximum-likelihood and Bayesian approaches identified shifts in diversification rate and possible links to character evolution. We inferred the ancestral environment for Viburnum and changes in diversification dynamics associated with subsequent biome shifts. Viburnum probably diversified in tropical forests of Southeast Asia in the Eocene, with three subsequent radiations in temperate clades during the Miocene. Four traits (purple fruits, extrafloral nectaries, bud scales and toothed leaves) were statistically associated with higher rates of diversification. However, we argue that these traits are unlikely to be driving diversification directly. Instead, two radiations were associated with the occupation of mountainous regions and a third with repeated shifts between colder and warmer temperate forests. Early-branching depauperate lineages imply that the rare lowland tropical species are ‘dying embers’ of once more diverse lineages; net diversification rates in Viburnum likely decreased in these tropical environments after the Oligocene. We suggest that ‘taxon pulse’ dynamics might characterize other temperate plant lineages.

本研究以近乎完整的被子植物（angiosperm）荚蒾属（Viburnum）系统发育为基础，评估其谱系分化速率，并探究驱动辐射演化的潜在形态与生态因子。研究采用最大似然法（Maximum-likelihood）与贝叶斯方法（Bayesian approaches），识别出分化速率的转变及其与性状演化的潜在关联。我们推断了荚蒾属的祖先生境，以及伴随后续生物群区转移（biome shifts）的分化动态变化。荚蒾属可能起源于始新世东南亚的热带森林，中新世时期其温带支系先后发生三次辐射演化。四项性状——紫色果实、花外蜜腺（extrafloral nectaries）、芽鳞（bud scales）与具齿叶片（toothed leaves）——与更高的分化速率呈显著统计关联。但我们认为，这些性状不太可能直接驱动分化。相反，前两次辐射演化与山地生境的定植相关，第三次则与冷暖温带森林间的反复转移存在关联。早期分化的贫乏谱系表明，现存稀有的低地热带物种是昔日多样谱系的‘垂死余烬’；渐新世之后，荚蒾属在这类热带生境中的净分化速率大概率出现下降。我们推测，‘类群脉冲’动力学（taxon pulse dynamics）可能也是其他温带植物支系的演化特征。