The Amazon basin is home to around 80,000 species of rainforest plants. Some 16,000 of these species are trees, while other species grow as shrubs, bushes and vines, combining to create a wildlife-filled environment.
With new plant species still being discovered on a regular basis, the Amazon rainforest is one enormous expanse of greenery, accounting for around 20% of the world’s entire cover of natural forest. Scientific studies have shown that a single square kilometer of the Amazon basin can harbor more than 90,000 tons of living plant matter.
The rainforests of the Amazon are filled with countless amazing plant species, many of which engage in symbiotic relationships with other species. One remarkable tree, the tangarana (Triplaris americana), also known as the “devil tree”, relies upon the ants it hosts to protect it from the threat of foreign invasion.
Although its slender trunk may have a diameter of just 30 centimeters (12 inches), the tangarana tree can grow up to 30 meters (100 feet) in height. Its smooth bark is a dappled gray color, and its oval or oblong leaves can measure up to 40 centimeters (16 inches) in length and 20 centimeters (8 inches) in width. When in bloom, it can be identified by its beautiful pink flowers, the males of which are around 2 millimeters (0.08 inches) long, while the female flowers measure up to 5 millimeters (0.19 inches) in length. The tangarana tree’s female flowers far outnumber their male counterparts.
At first sight, the tangarana looks very similar to other rainforest trees; however, upon closer inspection small holes can be seen along its trunk and branches. These holes are used by ants. The tangarana is what is known as a myrmecophyte (literally, an “ant plant”), a species that lives in a mutualistic association with colonies of ants. Myrmecophyte species like the tangarana live in a totally interdependent relationship with the particular species they host. In the case of the tangarana, this means that neither the tree nor the ants it is home to can survive on their own.
The tangarana is also commonly known as a “novice” tree, because only someone unfamiliar with the species would touch it. The ants that inhabit the tangarana tree are a species of fire ant (Pseudomyrmex triplarinus), and they are highly aggressive and possess a powerful sting. Without the nesting spaces and food source provided by the tangarana, these fire ants would be incapable of continuing their existence.
In its trunk and branches, the tangarana tree possesses internal structures specifically adapted for the habitation of the ants it hosts, together with the scale insects kept by the fire ant colony. These scale insects draw sugary sap from the internal structures of the tree, upon which the ants then feed, in what is yet another symbiotic relationship made possible by the tangarana. Fire ants are believed to identify their host and distinguish it from other Amazon trees species through surface chemicals produced by the tree. An average colony of these venomous ants will tend to number around 10,000 individuals.
In return for shelter and food, fire ants respond aggressively to foreign invaders or any disturbance of the host tree, protecting it against predation by other insects and animals. In humans, a sting from the Pseudomyrmex triplarinus ant will cause the fingers to swell and result in red flushes along the entire arm. In addition to attacking potential threats to their home, fire ants also clear vegetation from the base of the host tree, thereby granting it a competitive advantage in the battle for light waged by all Amazon tree species.
Among the indigenous Machiguenga and Ese Eja peoples of southeastern Peru’s forests, the tangarana is known as the “justice tree”, because traditionally wrongdoers were tied to its trunk with lianas and subjected to repeated stings from its colony of fire ants.