Data from: Ant mutualism increases long-term growth and survival of a common Amazonian tree

How ecological context shapes mutualistic relationships remains poorly understood. We combined long-term tree census data with ant censuses in a permanent 25-ha Amazonian forest dynamics plot to evaluate the effect of the mutualistic ant Myrmelachista schumanni (Formicinae) on the growth and survival of the common Amazonian tree Duroia hirsuta (Rubiaceae), considering its interactions with tree growth, population structure, and habitat. We found that the mutualist ant more than doubled tree relative growth rates and increased odds of survival. However, host tree size and density of conspecific neighbors modified the effect of the ant. Smaller trees hosting the mutualist ant consistently grew faster when surrounded by higher densities of conspecifics, suggesting that the benefit to the tree outweighs any negative effects of high conspecific densities. Moreover, our findings suggest that the benefit afforded by the ant diminishes with plant age and also depends on the density of conspecific neighbors. We provide the first long-term large-scale evidence of how mutualism affects the population biology of an Amazonian tree species.

生态背景如何调控互利共生关系，这一问题迄今仍未得到充分阐释。本研究将长期树木普查数据与蚂蚁普查数据相结合，依托一处永久25公顷亚马逊森林动态监测样地，针对亚马逊常见树种硬毛杜罗木（Duroia hirsuta，茜草科Rubiaceae），考量其与树木生长、种群结构及栖息地的相互作用，评估互利共生蚁类舒曼蚁（Myrmelachista schumanni，蚁亚科Formicinae）对该树种生长与存活的影响。研究结果显示，该互利共生蚁可使树木相对生长速率提升一倍以上，同时提高树木的存活概率。但宿主树木的体型大小以及同种邻株密度，会调控该蚂蚁的作用效果。当被较高密度同种邻株环绕时，携带该互利共生蚁的幼树始终生长更快，这表明树木获得的收益超过了高同种密度带来的负面影响。此外，本研究结果表明，该蚂蚁所提供的收益会随植物年龄增长而减弱，且同样取决于同种邻株的密度。本研究首次提供了长期大尺度的实证证据，阐明互利共生如何影响亚马逊树种的种群生物学特性。