Dense branching and spines are common features of plant species in ecosystems with high mammalian herbivory pressure. While dense branching and spines can inhibit herbivory independently, when combined, they form a powerful defensive cage architecture. However, how cage architecture evolved under mammalian pressure has remained unexplored. Here we show how dense branching and spines emerged during the age of mammalian radiation in the Combretaceae family and diversified in herbivore-driven ecosystems in the tropics. Phylogenetic comparative methods revealed that modern plant architectural strategies defending against large mammals evolved via a stepwise process. First, dense branching emerged under intermediate herbivory pressure, followed by the acquisition of spines that supported higher speciation rates under high herbivory pressure. Our study highlights the adaptive value of dense branching as part of a herbivore defence strategy and identifies large mammal herbivory as a major selective force shaping the whole plant architecture of woody plants.

密集的分枝和刺是哺乳动物食草压力较高的生态系统中植物物种的共同特征。虽然密集的分支和刺可以单独抑制食草动物，但当它们结合在一起时，它们会形成强大的防御笼结构。然而，笼子结构如何在哺乳动物的压力下进化仍有待探索。在这里，我们展示了在哺乳动物辐射时代，君子科家族如何出现密集的分枝和刺，以及如何在热带草食动物驱动的生态系统中实现多样化。系统发育比较方法揭示了现代植物防御大型哺乳动物的结构策略是通过逐步过程进化的。首先，在中等食草压力下出现密集的分枝，然后获得在高食草压力下支持更高物种形成率的刺。我们的研究强调了密集分枝作为草食动物防御策略一部分的适应性价值，并将大型哺乳动物草食性确定为塑造木本植物整个植物结构的主要选择力量。