This report first published by Marijuana Moment, 12 June 2025.

New research on cannabis genetics suggests that incentives in the legal marijuana market—such as the desire for plants to mature faster and produce more cannabinoids for extraction—may be leading to a decline in biodiversity of the plant worldwide.

A graduate thesis published this month combines observations about genetic trends in cannabis with interviews with dozens of plant breeders to explain the factors behind what author Caleb Y. Chen, at California State Polytechnic University (Cal Poly) Humboldt, describes as “the bottlenecking of Cannabis genetics.”

The review notes that while humans have been selectively breeding the cannabis plant for thousands of years, breeders in what it refers to as the “post-prohibition” era have optimized for a handful of traits, such as a high proportion of flowers as opposed to stalks or leaves, maximum cannabinoid content, a “desirable suite” of aromatic terpenes and a reproducible chemical profile.

That hasn’t always aligned with connoisseur preferences, but it’s made economic and regulatory sense sense. Citing interviews with growers in a 2021 paper, Chen writes that “their preference for High THC content in cultivars ‘was due to state testing regulations and a misinformed consumer base, rather than grower partialities.'”

So-called genetic bottlenecking isn’t unique to cannabis, the paper acknowledges, but is a common occurrence among agricultural crops. Nevertheless, research indicates that wild cannabis varieties are effectively a thing of the past.

“Recent genetics studies of Cannabis collections continue to suggest that wild specimens of Cannabis have gone extinct and existing ‘wild’ cannabis plants are feral escapees of domesticates,” the paper says, noting that wind pollination and other factors have “eliminated wild specimens from the genepool.”

Wind pollination also threatens to “wipe out landrace populations with ‘contamination’ from pollen via modern hybrids, therefore further bottlenecking Cannabis genetic diversity on a global scale,” the research found. “This has been reported from Morocco but also in Jamaica, Mexico, Thailand…and even parts of India.”

“Even without the human aspect of added Prohibition, more so than other crops, genetic bottlenecking is a real and present problem for Cannabis,” it adds.

“In 2025,” Chen writes, “just a handful of Cannabis cultivars are grown at all levels of the Post-Prohibition landscape. Most products are produced from just a handful of Cannabis cultivars which the large part of the market now considers to be generic agricultural commodities, perfectly suitable with each other.”

“Craft Cannabis,” the thesis continues, “besides being a marketing term,” is now “a counterculture within the industry.”

“These results may be meaningful in highlighting the role of government action on declining genetic diversity in the worldwide Cannabis market—and its impacts on the medicinal potential and therapeutic index of available Cannabis products.”

The paper calls the future for cannabis genetics “an open question,” noting that modern cannabis genetic bottlenecking is still “little explored.”

Based on interviews with growers, it reports that some feel popular metrics for cannabis fail to capture everything about what’s responsible for a marijuana high.

“As an example,” writes Chen, “Dr. Grinspoon is a particular cultivar that multiple breeders felt was special and not properly studied due to its long flowering time of up to 24 weeks.”

“It’s a perfect example of a plant that like…there’s something else in there that we’re not testing for,” one grower said. “And there has to be…because it’s just so incredibly different and pungent in that different way that there must be something in there that is not being described in the lab results at this point.”

To be sure, amid an upswing in marijuana research in the post-prohibition era, researchers are still unlocking new secrets about the cannabis plant. Researchers earlier this year, for example, announced that they successfully identified a new cannabinoid—cannabielsoxa—produced by the marijuana plant as well as a number of other compounds “reported for the first time from the flowers of C. sativa.”

Other research in 2023, published by the American Chemical Society, identified “previously undiscovered cannabis compounds” that challenged conventional wisdom of what really gives cannabis varieties their unique olfactory profiles.

The new paper notes that many breeders, in contrast to “ideotype breeding, which focuses on lab-measured physiological traits,” also consume the cannabis they grow to make final decisions on what’s best. “This evaluation step is arguably unique to the Cannabis breeding process and cannot be easily mechanized or automated,” it contends.

Other factors, like the rise of commercial marketing of cannabis strains, further complicate efforts to correctly identify genetics by creating “an incentive…for cultivators to misrepresent the linguistic labels used to describe their Cannabis genetics especially at the stage after it has been cultivated and as now being sold,” the thesis says.

“In my analysis,” Chen writes, “I’ve found that one of the effects of the Post-Prohibition landscape is a link between Cannabis regulation, falling Cannabis price, and falling Cannabis genetic diversity. As the Post-Prohibition landscape develops, the risk premium drops as does Cannabis‘s market value. All else equal, this leads Cannabis cultivators to prefer plants which yield more – which provide more saleable output.”

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