Enigmatic tree species rediscovered in the heart of the Amazon after 86 years

The finding by researchers at the Rio de Janeiro Botanical Garden helps to complete the puzzle of legume evolution.

By Marcus Falcão

Androcalymma glabrifolium is the only species in its botanical genus, one of the least known within the important and diverse legume family. This species of tree had only been observed once before, when it was discovered in 1936 by Russian scientist Boris Krukoff on an expedition to the upper Solimões River, in the state of Amazonas, close to the border with Colombia and Peru, an area virtually unknown to science. And in the 86 years that followed, the species was never found again and was even considered possibly extinct.

In December 2022, a new expedition was made to the region where Androcalymma had first been seen. Researchers Marcus Falcão, Vidal Mansano (JBRJ) and Guilherme Silva (Unicamp) set out to try and find this rare species again. Traveling by plane, car, as well as large and small boats, the researchers were able to reach the region of the Igarapé Belém, one of the tributaries of the majestic Solimões River, having obtained the authorizations of FUNAI and the indigenous chiefs of the region, which is now part of the Évare I indigenous land, of the Ticuna people, who played an essential role in the expedition with their immense knowledge of the environment and its flora. 

As well as dozens of other rare plant species, the researchers managed to find a population of several trees of the enigmatic Androcalymma. Trees over 40 meters tall were photographed for the first time and samples of leaves, flowers and fruit were collected. Many of its morphological characteristics were unknown, such as the fruits and the color and shape of its flowers, as well as its evolutionary relationship with other legumes since its DNA had never been analyzed.

The researchers published this study in a scientific article in the July 2023 issue of the international journal Phytotaxa. In this research, several novelties about Androcalymma were described and the species' DNA was sequenced, positioning it on the legume evolutionary tree, one of the last major pieces of the evolutionary puzzle still missing for this group of plants. 

The article, which is also co-authored by Leandro Cardoso Pederneiras (JBRJ), also highlights the importance of the environmental protection provided by indigenous lands which, as well as being essential for the existence of traditional peoples, also helps to preserve fauna and flora, as is the case with Androcalymma, identified as a critically endangered species. This further highlights the importance of policies to defend indigenous lands and the need to support new research into Amazonian flora, which still contains many mysteries to be unraveled.