Current Biology_human influence in nuts_

Long-term Human Influence on Bertholletia excelsa in the Amazon Basin

Overview

• Study Focus: Investigation of long-term human impact on the demography and genetic diversity of the Brazil nut tree, Bertholletia excelsa.

• Key Insights:

  • New genome assembly provides insight into genetic diversity.

  • Decline in genetic diversity noted since the Late Pleistocene.

  • Geographic structure reflects Indigenous management practices.

  • Emphasizes importance of historical knowledge for current genetic diversity management.

Research Team and Correspondence

• Authors: Hua Wang, Victor Caetano-Andrade, Nicole Boivin, among others.

• Correspondence: detlef.weigel@tuebingen.mpg.de, roberts@gea.mpg.de.

Importance of Bertholletia excelsa

Ecological Significance

• Role in Ecosystem:

  • Part of a limited group of hyperdominant trees in the Amazon that are crucial for ecosystem functions, such as nutrient cycling and rainfall production.

  • Large edible seeds serve as an essential non-timber product.

Historical Context

• Indigenous Relationship:

  • Brazil nut trees were likely dispersed and managed by Indigenous populations for over 13,000 years.

  • The interplay between the genetic structure of Brazil nuts and past human land use is largely unexplored.

Genetic Diversity Analysis

Methods

• Sampling: A total of 270 Brazil nut individuals collected from sites with varying archaeological evidence across the Amazon.

• Genome Assembly: A comprehensive genome size estimated at 570 Mb with high heterozygosity.

• Genome Sequencing Techniques: Utilized PacBio and ddRAD-seq for effective genetic diversity studies.

• Genetic Diversity Findings:

  • Limited genetic differentiation observed across populations indicating past human dispersal.

  • Significant correlation between genetic diversity and historic human management practices.

Key Results

• Decline in Genetic Diversity: Notable decrease since the Late Pleistocene, potentially linked to climate change and ecological shifts from open to denser forests.

• Impact of Human Management: Evidence suggests traditional management practices enhanced gene flow and genetic diversity in certain areas.

Demographic History

Evidence of Human Activity

• Site Overview: Research conducted in Tapirape-Aquiri National Forest, Tefe National Forest, and Jau National Park.

• Findings:

  • Genetic diversity levels were influenced by the historical presence of Indigenous and colonial management practices, notably in areas of terra preta (dark earth) indicating past anthropogenic influences.

  • Younger populations showed genetic exchanges attributable to human activities, in contrast to older, unmanaged populations.

Challenges and Management Strategies

Current Threats

• Genetic Diversity Loss: Deforestation and fragmentation currently threaten the genetic diversity of Brazil nut populations.

Recommendations

• Active Management Practices:

  • Encouragement of traditional agroforestry practices to balance ecological sustainability with economic harvesting objectives.

  • Seeking to reverse declines in genetic diversity and enhance resilience to ongoing environmental changes.

Conclusion

• Research Implications: This study underscores the critical connection between historical human interactions and genetic diversity, advocating for integrating archaeological and genomic data in contemporary management strategies.

• Future Research Directions: Further studies are needed to explore the interaction of human practices and genetic variation across other regions and tree species in the Amazon.

Summary: Human Influence on Brazil Nut Trees

Study Focus: This research investigates the long-term human impact on the Brazil nut tree (Bertholletia excelsa) in the Amazon Basin.

Key Findings:

• New genetic studies reveal changes in the genetic diversity of Brazil nut trees.

• A decline in genetic diversity has occurred since the Late Pleistocene (about 12,000 years ago).

• Indigenous management has influenced the genetic structure of these trees.

Importance of Brazil Nut Trees:

• Essential for the Amazon ecosystem, aiding nutrient cycling and rainfall production.

• Large seeds are vital non-timber products for local communities.

Historical Impact:

• Indigenous peoples have managed Brazil nut trees for over 13,000 years, influencing their genetic makeup.

Research Methods:

• Analyzed 270 Brazil nut samples from various locations in the Amazon using advanced genome sequencing.

Main Results:

• Limited genetic differentiation suggests past human dispersal.

• The decline in genetic diversity may be linked to climate change and shifts to denser forests.

Management Challenges:

• Current threats include deforestation, which jeopardizes genetic diversity.

• Recommendations promote traditional agroforestry practices for ecological sustainability and economic benefits.

Conclusion: This study emphasizes the critical relationship between human activity and the genetic health of Brazil nut trees, advocating for integrating historical and genomic data in management strategies.