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2023 Study: Clarifying Cannabis Classifications with Genetics

Updated: Nov 24, 2023

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Clarifying Cannabis Classifications Study

A 2023 study entitled "Genomics-based Taxonomy to Clarify Cannabis Classification" that was published in the Canadian journal Genome presented a review of "contemporary studies, many of which present strong cases for a single phenotypically diverse species in the genus, that we hope will help advance this ongoing debate."

A cannabis joint burning in an ashtray.
Controversial cannabis has many names.

The study reported that cannabis has served humans since 8,000 BC, when it emerged from Central and Eastern Asia. "The species is frequently classified and regulated based on the quantity of psychoactive cannabinoids produced and has been given many informal names to refer to different commercial and medicinal uses," noted the scientists.

"The study reported that cannabis has served humans since 8,000 BC, when it emerged from Central and Eastern Asia."

The research reported that most countries that allow cannabis regulate it according to the volume of delta-9 THC present. Hemp is defined as plants that feature less than 0.3 percent delta-9 THC, while subjects that produce more than this are considered cannabis (marijuana). "THC has been the main point of focus for governments crafting legislation governing cannabis, despite the fact that cannabis produces over 120 different cannabinoids," noted the study's authors.

Jean-Baptiste Lamarck
Jean-Baptiste Lamarck loved indica.

Cannabis Taxonomic Evolution

Clarifying Cannabis Classifications. The study reported that the "taxonomic classification" for cannabis is controversial. "Due to its centuries of use and informal breeding, present-day cannabis varieties represent hybrids of different genotypes with an incredibly diverse gene pool resulting in diverse phenotypes," explained the scientists.

Jean-Baptiste Lamarck & Indica

The study explained that, in 1785, Jean-Baptiste Lamarck, a French academic and biologist, introduced the concept of indica, which he distinguished from sativa based on "various morphological features, including a smaller height, woodier stems, alternate ramifications of the branches, narrow leaflets, and a villous calyx in the female flowers."

In 1785, French biologist Jean-Baptiste Lamarck introduced the concept of indica, which he distinguished from sativa based on "various morphological features."

Lamarck was the first to propose a taxonomy populated by two cannabis species, sativa and indica. Later, in 1940, a taxonomy was proposed based on morphology that involved two species, indica and sativa, which involved several subspecies, including proles, varieties, and forma. In 1950, a two-species system was proposed involving cannabis sativa and cannabis ruderalis (first introduced in 1924).

1970s Cannabis Taxonomic Proposals

In 1971, scientists measured the cannabinoid content of nine different cannabis samples and, as a result, proposed a two-way chemical classification "based on combined physical and chemical characteristics, allowing to differentiate between drug-type and fiber-type cannabis sativa."

In 1976, two scientists proposed a taxonomic grouping of cannabis that, like previous proposals, considered the plants physical characteristics and geographical distribution. However, this new proposal also considered the plant's THC content (its chemotype). "In this model, C. sativa is first divided into two varieties, either hemp or drug type, which are further separated into two groups: wild and domesticated," reported the scientists.

A woman smokes a cannabis joint.
Cannabis: One, two, or three species?

Clarifying Cannabis Classifications Conclusions

The study's authors made the following conclusions from their data and analysis.

"In recent years, the field of taxonomic classification has made significant strides, particularly in the use of genomic data to infer phylogenetic relationships. While traditional morphological and phenotypic methods have been successful for many species, they have proved inadequate for resolving the classification of certain taxa, such as Cannabis.

"The taxonomy of Cannabis is a divisive matter with various hypotheses, as has been discussed in this review."

"However, the use of genomic tools and techniques has enabled researchers to identify genetic variations and differentiate between species and subspecies. The increasing accessibility and affordability of these techniques have helped to shed light on the challenging taxonomy of Cannabis. The conventional taxonomy of Cannabis is challenging due to wind-pollination, the heterozygous nature of the plants, current growing practices and incomplete domestication paired with poorly tracked breeding pedigrees.

"The taxonomy of Cannabis is a divisive matter with various hypotheses, as has been discussed in this review. Precise taxonomic information is crucial for the study of Cannabis and in its absence, we risk the loss of genetic diversity as historic landraces may not be identified and preserved.

A woman holds growing cannabis leaves in a garden in her hand.
What do you call it?

"The emerging evidence from contemporary genomic sequencing and other molecular techniques outlined in this review strongly supports the hypothesis of a highly diverse monotypic species, and older hypotheses positing multiple species or subspecies now appear less likely in light of the emerging data.

"Although challenging, we believe that the taxonomy of the species is becoming clearer and will continue to benefit from advances in genomic tools, as we have demonstrated in this review. Ultimately, the confirmation of a highly diverse monotypic species of cannabis will be a significant contribution to the plant's taxonomic history and will enable the preservation of valuable genetic diversity."

View the original study.

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