Deforestation alter the evolution of the palms, reveals study

Research published in Science shows the relationship between birds, palm trees and human action
Karin Solomon


Tucano chickpeas and black-jacutinga birds are important seed dispersers of palm-juçara (Photo: Lindolfo Edson Souto and Endrigo / Disclosure Science)

The evolution process is slow, normally takes thousands and thousands of years. But in a few hundred millennia evolution leaps forward. It could be a movie of X-Men, but a search of the scientific journal Science. The juçara palm (Euterpe edulis), the size of its seeds and its relationship with large birds were objects of research led by an expert in biological sciences Mauro Galetti, Universidade Estadual Paulista (UNESP) in Rio Claro, published on May 31 in Science.

Each species has a large genetic variety. There are two identical individuals. This allows a species to better survive various environments. In the case of palm juçara, there are plants with seeds large, medium and small. This diversity has always existed in nature, more specifically in the Atlantic Forest habitat juçara palm. Also there were always birds large and small, while feeding these seeds, dispersed by other environments, ensuring its reproduction. Each tree produces on average three kilograms or more of a thousand seeds. Guan, toucans, crows and guans, large birds, feed on larger fruits. Already thrushes, by having a beak and small, prefer the little fruits.

The interaction between these birds and palm tree, called mutualism, was being built over millions of years. But sufficed 100 years of human activity to destroy the relationship of life. The devastation and dismemberment of the Atlantic reached high levels, with only 5% to 7% of the original forest. The larger birds were wiped out by deforestation and hunting. If there are no birds to disperse the fruit, they fall close to the foot and by competition with the mother plant can not grow. Thus, the palm trees with smaller seeds were more likely to reproduce in smaller forests.

Over five years, the researchers collected more than 9000 seeds of 22 populations of palm trees, scattered in small fragments and continuous forest areas of the Atlantic between the Paraná and southern Bahia. In seven of them (six in Sao Paulo and one in Rio de Janeiro) there was large seeds, just areas that are impacted by human longest.

Risks to the palm juçara

"This is the first time a study proves human interference in a process of mutuality - mutual dependence of two species in the case and the palm trees," says Peter Brancalion, professor Esalq / USP.

But this is not the first threat to human palm juçara, very present in Brazilian cuisine. This plant is endangered because of illegal cutting of the palm. Once cut, the juçara does not regenerate more - different varieties acai pupunha and which produce logs and many have the ability to spring back.

The decrease in seed size also interfere with their chance of survival. In the early days of existence, the plant is highly dependent on nutrients from seed. The smaller the seed, the smaller the amount of nutrients and has a lower chance of survival. According Brancalion, 99% plant mortality occurs in this initial phase.

Smaller fruits are also less able to retain water. Like many other species of tropical rainforests, the juçara seeds are adapted to environments with wet soil and are vulnerable in drought. As juçara seeds are dispersed mainly between the months from March to June, a period when the dry season begins, the smaller seeds are even more fragile.

Source: Globo Rural magazine