How Trees Utilize Rivers to Expand from the Amazon to the Atlantic Tropical Forests

As a lung of the planet, the Amazon is a real biodiversity treasure. The Amazon forest is home to thousands of species of more impressive trees than each other like the kapokier which can reach up to 70 meters in height.

We know that species of trees have spread from the Amazon to the Atlantic tropical forests for millions of years. However, the researchers had so far not discovered the secret of this colonization of the Atlantic forests of South America by the Amazon forest.

Hydrochoria is the secret of the dispersion of trees in the Amazon

A new study published in the Revue Proceedings of the Royal Society B: Biological Sciences has pierced the mystery of this arboreal colonization. The researchers discovered that the Amazon rivers serve in a way as “highways” for trees.

The dissemination of water seeds, also called hydrochary, is particularly effective in the case of the Amazon forest. The seeds of these trees float on the surface of the water for long periods thanks to their waterproof envelope.

They are thus driven by rivers, rivers and all other water currents. This explains why we find the same species of trees in the Amazonian forest and in the Atlantic tropical forests when they are separated by hundreds of kilometers.

This colonization was made on several generations of trees

In fact, this colonization mechanism intrigued the researchers all the more than a region that is too arid for these trees separated the two types of forests. An ancient theory therefore suggested that the trees had crossed South America when this dry region was much more humid.

“” Rather than exchanging species of trees for specific wet periods in the past, we have found that the species have been dispersed constantly over time “Said Dr. James Nicholls, principal author of the study of the Royal Botanical Garden of Edinburgh.

Of course, this hydrocomia is not literally a highway. The process is even particularly slow. Generations of trees have gradually pushed ” Along the rivers that cross the dry ecosystems of Brazil Adds Dr. James Nicholls.

Several species of trees have successfully rooted hundreds of kilometers from their origin

To arrive at this conclusion, the researchers studied genetics of 164 species of inga trees. Trees of this kind are common in the forests of Latin America. They thus rebuilt “the family tree” thanks to their DNA.

This made it possible to highlight the moment when the species separated from their ancestors to move through the continent.

The researchers thus identified 16 to 20 cases of species of trees which migrated from the Amazon to Atlantic forests where they successfully rooted. They also noted that this dispersion did not only occurred during periods of strong humidity.

The Atlantic tropical forest has ” 3,000 more plant species than the Amazon »»

In addition, only one or two species of trees have spread in the other direction, that is to say from Atlantic forests to the Amazon.

As Professor Toby Pennington explains who is also a study author, that ” We also learn something fundamental about the history of the incredible biodiversity of the Atlantic tropical forest, which contains about 3,000 more plant species than the Brazilian Amazon ».

It is crucial to protect these tropical forests in the short term, but also to maintain the connections between them in the long term. Especially since only 20 % of the tropical Atlantic forest now remain intact.

Source: Iflscience