Genetic legacy of the Brazil nut tree has been altered by human activity

The Brazil nut tree (Bertholletia excelsa) is a vital part of the Amazon’s rich biodiversity, but its genetic diversity has faced centuries of disruption.

Factors such as European colonization, extensive deforestation, and the extinction of large seed-dispersing animals like the giant sloth have all played a role in its decline.

The Brazil nut tree is also a symbol of ecological resilience, economic sustenance, and the intricate web of life within the rainforest. But now, its future is at stake as human activities are constantly shifting the ecology of the Amazon Basin.

Genomic data from Brazil nut trees

A team of researchers recently embarked on a mission to investigate the genetic diversity and population dynamics of Brazil nut trees.

“This research provides an amazing opportunity to study how human actions, even in the distant past, have affected genetic makeup in a wild species over short time scales,” noted Detlef Weigel, an expert at the the Max Planck Institute for Biology Tübingen.

The scientists used up-to-date genomic techniques to analyze a total of 270 Brazil nut tree samples. These samples, each with known archaeological evidence, were collected from various locations.

The result of this analysis was a detailed genomic data sheet that identified over 126,000 genetic variants in the Brazil nut tree’s genome. The data is a treasure trove of insights into the genetic health and adaptability of the species.

Genetic diversity of Brazil nut trees

The study suggests that, when compared to the diversity of other species, there has been a steep decline in the genetic diversity of Brazil nut trees over the past 20,000 years. But, it’s not all gloom and doom.

Areas that have been managed by Indigenous communities show more complex genetic backgrounds, revealing a deep connection between plant life and Indigenous land stewardship.

For example, younger trees (less than 200 years old) in the Tefé National Forest (TEF) show a greater diversity of genes. This is thanks to their adaptation to previous natural disturbances and to the management approaches of local communities that have led to genetic resilience.

This exemplifies how traditional ecological practices can uphold the genetic diversity and health of a species while providing a model for sustainable management.

Victor Caetano-Andrade, a postdoctoral researcher in the Department of Coevolution of Land Use and Urbanisation at the Max Planck Institute of Geoanthropology, shared his insight.

“We aimed to bridge gaps in our understanding of the long-term anthropogenic influences on forest ecosystems. Our findings demonstrate how Indigenous land management practices play a significant role in maintaining the genetic diversity of Brazil nut populations,” said Caetano-Andrade.

Strengthening collaboration and conservation

This innovative study highlights the crucial partnership between scientists and Indigenous land stewards. By leveraging their historical ecological knowledge, we can create more inclusive and effective conservation policies.

Looking ahead, the scientists plan to broaden their investigation to more regions and additional species within the Amazon rainforest.

The ultimate goal is to develop comprehensive conservation frameworks that protect Brazil nut trees and bolster the ecosystem’s resilience.

Ecological and economic impacts

The loss of genetic diversity in Brazil nut trees affects more than just the species itself. The impacts extend to other aspects of the rainforest ecosystem, as well as to local economies.

The Brazil nut tree is a keystone species that plays a crucial role in supporting biodiversity. These trees provide food and shelter for countless organisms – ranging from pollinators like orchid bees to large, fruit-eating mammals.

Reduced genetic diversity weakens the tree’s resilience to climate change, pests, and diseases, and increases the risk of population decline.

Moreover, this genetic bottleneck has economic consequences for communities that rely on Brazil nut harvesting as a primary source of income.

Declining tree health and lower yields could threaten a sustainable industry that has supported Amazonian livelihoods for centuries.

Maintaining genetic variation through conservation efforts and Indigenous land stewardship will be essential for safeguarding not only the species but also the ecological and economic stability of the region.

The full study was published in the journal Current Biology.

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