First published: 03 February 2026.
In the Brazilian Cerrado and tropical ecosystems worldwide, many plants employ a fascinating strategy: they produce sugar-rich droplets on their leaves or stems, known as extrafloral nectar. This nectar isn’t for pollinators – it’s payment for “bodyguards.” Ants drink the nectar and, in return, aggressively defend the plant against hungry herbivores.
However, as explored in a new review in Ecological Entomology, “Ant behaviour as a mediator of extrafloral nectary-based mutualisms: Interactions with nectar chemistry and environmental conditions”, this mutualism is far from simple. It is a dynamic relationship shaped by three critical forces.
First, nectar chemistry is a signal: plants don’t just serve sugar water; they can alter the chemical recipe (amino acids and secondary metabolites) in response to herbivory, effectively “calling” specific ant partners when they are under attack.
Image: A wasp visiting Banisteriopsis malifolia. This illustrates the complex network of visitors on EFN-bearing plants, highlighting potential trade-offs between defence and pollination.
Photo credit: Rodrigo do Rosario Nogueira
Secondly, ant personality matters: not all ants are good guards. Some are aggressive hunters, while others are timid nectar thieves. Moreover, aggressive ants can sometimes be too effective, accidentally scaring away the plant’s pollinators, leading to a trade-off between protection and reproduction.
Image: Fire resilience in the Brazilian Cerrado (burnt landscape).
Photo credit: Rodrigo do Rosario Nogueira
Thirdly, the environment rules: external factors like fire frequency and habitat fragmentation dramatically change the outcome. In the fire-prone Cerrado, for instance, fresh plant regrowth after a burn is a magnet for ants, creating a crucial window of protection for vulnerable tissues.
Image: Vegetation recovery one month later. The contrast illustrates the pulse of new resources that often drive ant-plant interactions.
Photo credit: Rodrigo do Rosario Nogueira
“We often think of ant-plant interactions as simple exchanges of sugar for protection, but this review highlights how complex and dynamic these partnerships really are.
To truly understand whether ants are helping or hindering plants, we must look at the “chemical dialogue” of the nectar, the distinct personalities of the ant species involved, and how environmental stressors like fire and climate change reshape these interactions in real-time.”
– Dr. Rodrigo do Rosario Nogueira
While we know the pieces of the puzzle, we rarely study them all together. This review suggests that future research needs to integrate chemical ecology with landscape-level experiments. We need to understand how global changes, such as warming climates and altered fire regimes, will disrupt these delicate alliances, potentially turning beneficial partners into ecological liabilities.
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