Diversity and genetic structure of mariri tucunacá (Banisteriopsis caapi) populations in the southern Brazilian Amazon rainforest

The Brazilian Amazon plays a vital role in global biodiversity, harboring species such as Banisteriopsis caapi, known for its cultural and medicinal significance. This study aimed to analyze the genetic diversity, with the use of ISSR (inter-simple sequence repeat) markers, of natural populations of mariri (B. caapi ethnovariety Tucunacá) in the Southern Amazon, as well as cultivated populations in agroforestry systems in Mato Grosso. The analysis revealed 92.3% polymorphism, with an average of 11.55 amplified bands per primer and a mean PIC of 0.466, considered moderately informative. Natural populations had greater genetic diversity (H = 0.323; I = 0.468) than cultivated ones (H = 0.164; I = 0.241), highlighting their role as genetic reservoirs. AMOVA indicated that 58% of the genetic variation occurs between populations, with low gene flow (Nm = 0.485) and strong genetic structuring (Fst = 0.582). The UPGMA (Unweighted Pair Group Method with Arithmetic Mean) dendrogram grouped populations into two main clusters, while Bayesian analysis identified three genetic clusters, reflecting geographic isolation and human management. Cultivated populations, particularly those at the Xingu Park Indigenous Territory, maintained significant genetic diversity, likely due to the use of seedlings from different origins. This study reinforces the importance of conserving natural populations, given increasing deforestation, and promoting sustainable management of cultivated populations to ensure species adaptability. Strategies such as in situ conservation and genetic diversity enhancement should be integrated to safeguard the ecological and cultural viability of B. caapi, ensuring the continuity of Ayahuasca’s traditional use by the communities dependent on this ethnovariety.