Martius and the Ant-Plants of the Amazon
During his travels through the Amazon, Martius observed that some plants had unusual structures in their leaves, which harbored colonies of ants.
By CRIA - Centro de Referência em Informação Ambiental
Renato Goldenberg & Fernando B. Matos
Reise in Brasilien, title page (1823) by Johann Baptist von Spix, Carl Friedrich Philipp von MartiusOriginal Source: Wikimedia Commons
In his book ‘Travels in Brazil,’ he described this association between ants and plants as follows: “Very curious are the habits of various ant species living in Melastomataceae plants. [...]"
Miconia macrosperma (= Tococa macrosperma) (October 23, 2011) by Renato GoldenbergCRIA - Centro de Referência em Informação Ambiental
"[...] The leaves of the genus Maieta have on their underside a two-compartment oblong bulb, and the petioles of the genus Tococa are swollen, forming a similar cavity. Inside, numerous societies of small red ants live, biting fiercely.”
Miconia macrosperma (= Tococa macrosperma) (October 23, 2011) by Renato GoldenbergCRIA - Centro de Referência em Informação Ambiental
These unusual structures, as described by Martius, are like balloons at the base of the leaves, with an internal space where ants reside.
At first glance, these structures might not be easy to see, just as the ants aren’t immediately visible. But they are there... Notice the slightly rough structure above the nearly black-blue fruit, which is consumed by birds.
Miconia macrosperma (= Tococa macrosperma) (October 23, 2011) by Renato GoldenbergCRIA - Centro de Referência em Informação Ambiental
When we turn the plant to see the underside of the leaves, these balloons become more visible.
Miconia macrosperma (= Tococa macrosperma) (October 23, 2011) by Renato GoldenbergCRIA - Centro de Referência em Informação Ambiental
Another thing happens when we turn the plant: the movement disturbs the ants, which emerge from their ant nests to defend the plant against a possible herbivore.
The ants exit through the ant nest entrance, located precisely at the convergence of the veins. This entrance/exit is only on the underside of the leaves.
The plant shown in these photos was described by Martius in 1832, before the start of Flora Brasiliensis. It is named Miconia macrosperma.
Encountering or brushing against this plant can be very painful... This can be beneficial for the plant: in exchange for providing shelter to the ants, it gains a super-efficient protection system against herbivores.
Martius saw other species with similar structures. All belong to the Melastomataceae family. In this family, the association with ants is quite common, but it does not occur in all species.
Tococa formicaria, figure (1832) by Carl Friedrich Philipp von MartiusOriginal Source: flickr
These structures were detailed with impressive precision, considering that this work was published in 1832.
Miconia tococa (= Tococa guianensis, = Tococa formicaria) (October 13, 2011) by Renato GoldenbergCRIA - Centro de Referência em Informação Ambiental
Like everything in botany, these structures have a name. They are called "formicaria".
Miconia tococa (= Tococa guianensis, = Tococa formicaria) (October 13, 2011) by Fabián MichelangeliCRIA - Centro de Referência em Informação Ambiental
“Formicaria” are true ant nests, where ants live, reproduce, and raise their larvae.
This Melastomataceae belongs to a newly described species (Miconia velazuelana, 2020), based on plants collected in Peru. In this case, it is the stem, not the leaf, that is hollow. Ants create an entry hole, and inside, the plant produces food bodies.
It’s not only Melastomataceae that have this association with ants. In Boraginaceae, for example, several species of Cordia also have "formicaria".
Miconia sp. (July 15, 2017) by Renato GoldenbergCRIA - Centro de Referência em Informação Ambiental
Every visitor to the Amazon gets the impression of how rare large animals are, and how there are many, many insects – especially ants, bees, wasps, and mosquitoes. Martius was one of the first scientists to describe these interactions between plants and ants.
Research and writing: Renato Goldenberg (UFPR) & Fernando B. Matos (CRIA)
Assembly: Fernando B. Matos (CRIA)
Review: Renato De Giovanni (CRIA)
References: Flora Brasiliensis (http://florabrasiliensis.cria.org.br/opus); Travels in Brazil (https://www2.senado.leg.br/bdsf/handle/id/573991); Nova genera et species plantarum, vol. 3 (https://www.biodiversitylibrary.org/page/744405).
Additional information: http://florabrasiliensis.cria.org.br/stories
Acknowledgments: Special thanks to Drs. Axel Mithöfer (Max Planck Institute for Chemical Ecology) and Fabian Michelangeli (NYBG), for permission to use their videos and photos.
*Every effort has been made to credit the images, audio, and video and correctly recount the episodes narrated in the exhibitions. If you find errors and/or omissions, please email contato@cria.org.br
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