Ants and Plants

Every Ant Tells a Story - And Scientists Explain Their Stories Here
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Complex symbioses have been fashioned among the thousands of species of ants and plants. Often these relationships are parasitic, with one exploiting the other and giving nothing in return. In other cases they are commensalistic, with one partner making use of the other but, as in the case of ants occupying hollow stems, neither harming nor helping it. But of maximum scientific interest, some symbioses appear to be mutualistic; in other words, both partners benefit from the association. To put the matter as briefly as possible, ants use cavities supplied by the plants for nest sites, as well as nectar and nutritive corpuscles given them as food. They in turn protect their plant hosts from herbivores, distribute their seeds, and literally pot their roots with soil and nutrients. There is abundant evidence, which we will review shortly, that some pairwise combinations of ants and plants have coevolved so that each is specialized to use the other's services. This mutualistic linkage has produced some of the most elaborate adaptations known in nature. (Holldobler and Wilson 1990).

Nelson et al. (2018) - Ant-plant interactions are diverse and abundant and include classic models in the study of mutualism and other biotic interactions. By estimating a time-scaled phylogeny of more than 1,700 ant species and a time-scaled phylogeny of more than 10,000 plant genera, we infer when and how interactions between ants and plants evolved and assess their macroevolutionary consequences. We estimate that ant-plant interactions originated in the Mesozoic, when predatory, ground-inhabiting ants first began foraging arboreally. This served as an evolutionary precursor to the use of plant-derived food sources, a dietary transition that likely preceded the evolution of extrafloral nectaries and elaiosomes. Transitions to a strict, plant-derived diet occurred in the Cenozoic, and optimal models of shifts between strict predation and herbivory include omnivory as an intermediate step. Arboreal nesting largely evolved from arboreally foraging lineages relying on a partially or entirely plant-based diet, and was initiated in the Mesozoic, preceding the evolution of domatia. Previous work has suggested enhanced diversification in plants with specialized ant-associated traits, but it appears that for ants, living and feeding on plants does not affect ant diversification. Together, the evidence suggests that ants and plants increasingly relied on one another and incrementally evolved more intricate associations with different macroevolutionary consequences as angiosperms increased their ecological dominance.

Topics

Ant Plants

References

  • Nelsen, M. P., R. H. Ree, and C. S. Moreau. 2018. Ant-plant interactions evolved through increasing interdependence. Proceedings of the National Academy of Sciences of the United States of America. 115:12253-12258. doi:10.1073/pnas.1719794115