The vast Amazon is globally recognized for its incredible diversity of trees, but until now it was not fully understood how this richness has developed and been maintained. A recent study has shed light on this mystery, highlighting the crucial role of hybridization and interaction with herbivores.
Hybridization and Herbivores: Keys to Amazonian Diversity
The research suggests that some tropical trees do not evolve in isolation. Instead, they experience genetic mixing through gene exchange between close species. This phenomenon strengthens their chemical defenses against insects that feed on their leaves, a crucial factor for biodiversity in the Amazon.
The study, which examined 461 individuals of the genus Inga, was published as a preprint in bioRxiv on June 20, 2026. In an environment as competitive as the rainforests, trees not only adapt to light and water; they must survive the constant attack of insects like caterpillars and beetles.
Herbivory, the consumption of plants by animals, especially insects, significantly influences which trees thrive. To counteract this, plants have developed chemical compounds that make it difficult for their leaves to be consumed.
The idea that tropical trees rarely hybridize is being reconsidered. Genetic mixing in the genus Inga, for example, could facilitate the exchange of genes related to chemical defense, similar to sharing a “survival manual” among species.
Not all trees hybridize indiscriminately. Species tend to form regional networks, known as “syngameons,” where genetic flow is controlled. The many species of Inga, which live in proximity and share predators, provide an ideal context to study these dynamics.
Researchers compared tree genomes with data on the abundance of herbivores, concluding that the renewal of herbivorous insects coincides with transfers of defense genes between species.
Defense genes do not act alone. They present themselves as groups that can move between species and be selected for their utility, depending on the herbivores present in the area.
The variability in insect communities, which change from place to place in the Amazon, is a key factor. Insects have short life cycles and evolve rapidly, complicating adaptation for long-lived trees. Here, hybridization could offer an advantage.
The study proposes that instead of relying on mutations within a single species, trees can benefit from genetic variations of nearby species, a true evolutionary shortcut.
The Amazon is more than a storehouse of biodiversity; it is an active evolutionary laboratory, where genetic exchange between species could be a driver of diversity.
This study, although not yet formally reviewed, suggests that the boundaries between species in the jungle are not as rigid as previously thought, which could enrich diversity rather than reduce it.
Conservation must consider not only individual species but also the communities and processes that facilitate these adaptations. Without these, the rich biodiversity of the Amazon could be at risk.
The full study is available at bioRxiv.
