Ants and Plants

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The degree of association between plants and ants varies greatly. On one end of a spectrum of ant plant interactions are ants that use a plant exploitatively or in a relatively benign manner. Plants at the opposite extreme are obligate mutualists that have co-evolved with an ant partner and provide specialized nesting and food resources. Other plants fall somewhere between these two types of interactions.

Holldobler and Wilson (1990) provided a summary of ant-plant interactions in Chapter 14 of The Ants (see the full text here), including the following excerpt: 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 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. You can continue to read more from The Ants about ant plants here.

Wilson and Hölldobler (2005) argued that interactions between ants and plants led to important changes in ant diversity and the evolution of ant life histories. This was driven by ecological change arising from plant diversification and the ant's utilizing plants for food and nest resources. These emerging and evolving changes allowed ants to expand their initial ecological success beyond what was a clade of predominately ground-dwelling predators.

Nelson et al. (2018) examined aspects of the evolutionary history of the relationships between ants and plants: 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.

Ant-Plant Topics

Plants provide resources to ants

Seed Dispersal by ants

Plant Rewards

  • Protection against herbivores
  • reducing plant competition

Ant Plants

References

  • Hölldobler, B. and Wilson, E. O. 1990. The Ants. Cambridge, Mass. Harvard University Press.
  • 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
  • Wilson, E. O. and B. Hölldobler. 2005. The rise of the ants: a phylogenetic and ecological explanation. Proc. Natl. Acad. Sci. U.S.A. 102:7411-7414. doi:10.1073/pnas.0502264102