Data from: Macroevolutionary assembly of ant/plant symbioses: Pseudomyrmex ants and their ant-housing plants in the Neotropics

Symbioses include some of the clearest cases of coevolution, but their origin, loss, or reassembly with different partners can rarely be inferred. Here we use ant/plant symbioses involving three plant clades to investigate the evolution of symbioses. We generated phylogenies for the big-eyed arboreal ants (Pseudomyrmecinae), including 72% of their 286 species, as well as for five of their plant host groups, in each case sampling >61% of the species. We show that the ant-housing Vachellia (Mimosoideae) clade and its ants co-diversified for the last 5 Ma, with some species additionally colonized by younger plant-nesting ant species, some parasitic. An apparent co-radiation of ants and Tachigali (Caesalpinioideae) was followed by waves of colonization by the same ant clade, and subsequent occupation by a younger ant group. Wide crown and stem age differences between the ant-housing genus Triplaris (Polygonaceae) and its obligate ant inhabitants, and stochastic trait mapping, indicate that its domatium evolved earlier than the ants now occupying it, suggesting previous symbioses that dissolved. Parasitic ant species evolved from generalists, not from mutualists, and are younger than the mutualistic systems they parasitize. Our study illuminates the macroevolutionary assembly of ant/plant symbioses, which has been highly dynamic, even in very specialized systems.

共生作用（symbioses）是协同进化（coevolution）最为清晰的例证之一，但其起源、丢失或是与不同伙伴重新组合的过程却鲜有研究能够得以推断。本研究以涉及三个植物演化支的蚁植共生体系为研究对象，探究共生作用的演化历程。我们构建了大眼树栖蚂蚁——伪切叶蚁亚科（Pseudomyrmecinae）的系统发育树，涵盖其286个物种中的72%；同时还构建了5个植物宿主类群的系统发育树，每个类群的物种采样率均超过61%。研究结果显示，供蚁栖息的金合欢属（Vachellia，含羞草亚科Mimosoideae）演化支与其共生蚂蚁在过去5 Ma间实现了协同分化，部分植物物种还被更年轻的植栖蚂蚁类群所定植，其中部分类群为寄生性蚂蚁。蚂蚁与塔奇加利属（Tachigali，云实亚科Caesalpinioideae）演化支之间看似存在协同辐射演化，随后该蚂蚁演化支发生了多轮跨宿主定植事件，最终被更年轻的蚂蚁类群所占据。供蚁栖息的Triplaris属（蓼科Polygonaceae）与其专性共生蚂蚁之间存在显著的冠群与茎群年龄差异，结合随机性状映射分析结果可知，该属的蚁栖结构（domatium）的演化时间早于当前占据该结构的蚂蚁类群，这暗示此前曾存在共生体系后又发生了解体。寄生性蚂蚁类群均由广食性蚂蚁演化而来，而非互利共生蚂蚁，且其出现时间晚于它们所寄生的互利共生体系。本研究阐明了蚁植共生体系的宏观演化组装过程——即便在高度特化的共生体系中，其演化历程也始终处于高度动态的变化之中。