Zhejiang Provincial Key Laboratory of Plant Evolutionary Ecology and Conservation, Taizhou University, Taizhou, China.
UMR AMAP, IRD, CIRAD, CNRS, INRA, Montpellier University, Noumea, New Caledonia.
Ann Bot. 2020 Jan 8;125(1):49-57. doi: 10.1093/aob/mcz131.
Our aim was to understand the environmental conditions of the emergence and radiation of early angiosperms. Such a question has long remained controversial because various approaches applied in the past have drawn conflicting images of early angiosperm ecology.
We provided a new perspective on the question by using support vector machines to model the environmental niche of 51 species belonging to ten genera of extant lineages that diverged early during angiosperm evolution (basal angiosperms). Then, we analysed the resulting pattern of niche overlap and determined whether this pattern deviates from what would be expected on the basis of a null model or whether it might mirror a legacy of a common primitive niche based on a phylogenetic reconstruction.
The niche of three-quarters of the species and all genera converged towards tropical montane cloud forests (TMCFs). The latitudinal pattern of basal angiosperm richness indeed culminated in the tropics, and the elevational pattern revealed a humpback curve peaking between 2000 m and 3500 m when accounting for the effect of area. At first glance, this diversity pattern does not significantly differ from null predictions. However, we revealed a tendency for the basal-most taxa to occur in TMCFs so that phylogenetic reconstructions indicated that the niche of the common ancestor of the sampled basal angiosperms had a probability of 0.85-0.93 to overlap with TMCFs.
Our new approach indicates that the environmental convergence of extant basal angiosperms towards TMCFs would reflect a legacy of an ancestral niche from which the least basal taxa would have diverged following a random pattern under geometric constraints.
我们的目的是了解早期被子植物出现和辐射的环境条件。由于过去应用的各种方法得出了相互矛盾的早期被子植物生态学图像，因此这个问题长期以来一直存在争议。
我们通过使用支持向量机来为属于早期被子植物进化（基被子植物）中分化较早的十个属的 51 个物种建模环境生态位，从而为这个问题提供了一个新的视角。然后，我们分析了由此产生的生态位重叠模式，并确定该模式是否偏离了基于空模型的预期，或者它是否可能反映基于系统发育重建的共同原始生态位的遗产。
四分之三的物种和所有属的生态位都趋向于热带山地云雾林（TMCF）。基被子植物丰富度的纬度模式确实在热带达到顶峰，而在考虑到面积效应的情况下，海拔模式揭示了一个驼峰曲线，在 2000 米至 3500 米之间达到峰值。乍一看，这种多样性模式与空值预测没有显著差异。然而，我们发现最基础的分类群倾向于出现在 TMCF 中，因此系统发育重建表明，所采样的基被子植物共同祖先的生态位有 0.85-0.93 的概率与 TMCF 重叠。
我们的新方法表明，现存基被子植物向 TMCF 的环境趋同将反映出一个祖先生态位的遗产，从这个生态位中，最基础的分类群在几何约束下以随机模式分化。
