We cannot distinguish wild coca plants from
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We cannot distinguish wild coca plants from

Coca leaves


coca leaves on a plant

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Credits: Natalia Przelomska/Molecular Biology and Evolution

A new article in Molecular biology and evolutionpublished by Oxford University Press, says that although the United Nations Office on Drugs and Crime has been collecting annual data on coca-growing areas in South America for decades – to monitor the establishment of illegal plantations and associated deforestation – scientists are unable to reliably distinguish between different types of coca plants. While identification is often based on leaf shape and size, this does not reflect the differences between coca varieties grown to extract the alkaloid cocaine (the active ingredient in the recreational drug), coca grown for traditional purposes, and coca plants growing in the wild.

South American coca has been a staple crop for many Andean and Amazonian communities for at least 8,000 years and still plays a vital role in the livelihoods of millions of South Americans today. People use its leaves, rich in active compounds (cocaine being just one of them), for cultural rituals, medicinal treatments, dietary supplements, and as a daily stimulant.

However, over the last half century, global demand for the alkaloid cocaine, due to the industrial extraction of this unique compound, has led to intensive agriculture of the plant and placed it at the center of armed conflicts and deforestation.

Coca belongs to the diverse genus Erythroxylumwhich includes over 270 different species, many of which are native to the American tropics. Of these, two cultivated coca species are found in mostly separate regions of northwestern South America. The most widely cultivated is Erythroxylum coca (Huánuco coca). Its Coca The variety is native to the humid mountain forests of the eastern Andean slopes of Peru and Bolivia, and its ipadou variety from the Amazon region. The least cultivated Erythroxylum novogranatense was historically cultivated in the dry valleys of the Cordilleras and Sierra Nevada de Santa Marta. Farmers cultivated its truxillense variety (‘Trujillo coca’) from the arid regions of northwestern Peru for traditional use and as a flavoring and stimulant additive for the soft drink Coca Cola.

The leaves of these two species, plants specifically cultivated by man and adapted to a human environment, were considered different from the leaves of closely related wild plants. Erythroxylum species by being smaller, rounder and softer. As for the distinction between the two, the leaves of E. coca are, in general, rounder than E. novogranatenseThis simple difference has been used in the field for coca plantation surveillance surveys.

But differences in leaf size and shape are not necessarily a reliable way to distinguish plant types. Despite extensive studies, the boundaries between cultivated coca varieties and their wild relatives are poorly defined. To address this challenge, the researchers used 1,163 leaf outlines from 342 digital herbarium specimens of wild and cultivated coca to extract data on size and shape. Using statistical methods, they showed that there is a high degree of overlap between species (and their varieties), which almost certainly led to misidentifications in the field. It also highlights the importance of using a variety of sources for plant classification. An inadequate classification system for coca can prevent the description of new varieties. This is relevant for plantations dedicated to cocaine extraction, but above all, it also contributes to the knowledge of the identity of varieties with improved characteristics for alternative uses, such as food supplements, fibers or pigments already obtained from these plants.

“We are rethinking the way we classify coca plants, whether cultivated or wild, by adding new data on their leaves and genes,” says Fabio Andrés Ávila of the New York Botanical Garden, one of the study’s authors. “This is important for Colombia’s biodiversity and for communities that use coca for traditional purposes, because it provides them with new sources of information about the plants they depend on.”

In this study, the researchers also investigated the genetic relationships between coca plants. They compared the results with existing taxonomic classification and assessed how well leaf shape and size matched genetics and whether this could be used to distinguish species and varieties. By examining coca genetic groups and using temporal models, they were able to estimate when different coca species and varieties first appeared. The results revealed that distinct coca plants began to evolve well before humans arrived in South America 15,000 years ago, although the timeline for the emergence of cultivated, cocaine-producing coca plants remains uncertain.

Although the shape and size of the leaves revealed characteristics specific to cultivated cocas, namely a generally rounder shape and a narrower base, the researchers found that these characteristics were not reliable for identification purposes. Instead, the study highlights the potential of genetic techniques as a more accurate method for identifying and monitoring coca populations.

“One of the main goals of our research is to provide a stable classification system and a comprehensive genetic database. This will allow us to confidently identify the different populations, varieties and species of cultivated coca and their wild relatives,” said Oscar Alejandro Pérez-Escobar of the Royal Botanic Gardens, Kew, another author of the study. “Such a system is essential for developing sustainable bioprospecting programs, and the coca bush has huge potential in this regard. But first it is essential to separate the valuable attributes of the plant from its association with recreational drugs, to reshape its perception and highlight its positive uses.”

The article, “Morphometrics and phylogenomics of coca (Erythroxylum spp.) shed light on its reticular evolution, with implications for taxonomy,” is available (midnight July 10th) at https://academic.oup.com/mbe/article-lookup/doi/10.1093/molbev/msae114.

Direct correspondence to:
Oscar Alejandro Perez-Escobar
Head of Research, Integrated Monograph Team
Royal Botanic Gardens, Kew
[email protected]

To request a copy of the study, please contact:
Daniel Luzer
[email protected]

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