New study reveals genetic vulnerabilities in mopane worms across Southern Africa

Southern Africa’s beloved mopane worm — a nutritional powerhouse and a lifeline for many rural communities — may be far more vulnerable than previously understood.

A new study led by Stellenbosch University (SU) has found striking gaps in the species’ genetic diversity across the region, raising red flags for its long-term survival.

Researchers from SU, the South African National Biodiversity Institute, the Botswana International University of Science & Technology and Namibia’s Ongava Research Centre analysed DNA from mopane worms in Namibia and the Limpopo River Basin.

Their findings, published in Conservation Genetics, show that despite the worm’s cultural and economic significance, “not enough information” exists on how populations are distributed or how resilient they are to environmental change.

“We offer the first look at how mopane worm populations are related and distributed across Namibia and the Limpopo River Basin, and how their numbers have changed over time,” said lead author Dr Barbara van Asch from SU’s Department of Genetics.

“Genetic data can help guide wildlife conservation by showing how different populations are related, how big they are and how they move or connect with one another.”

Van Asch said knowing where genetic diversity is strongest is key for future protection efforts.

“This genetic data is crucial for planning effective conservation strategies as concerns about the species’ sustainability have grown over the past two decades due to rising demand, habitat loss, climate change and a dramatic increase in cross-border trade between Botswana, South Africa and Zimbabwe worth millions of dollars.”

The worms — harvested widely for food and income — contain “three times more protein than beef or chicken”, plus high levels of calcium, iron and zinc, with less fat than conventional livestock.

Reports of overharvesting in Botswana, Namibia, South Africa and Zimbabwe have intensified fears that unsustainable collection and habitat loss could push the species closer to collapse.

The study found that populations from Namibia and the Limpopo River Basin “don’t share the same maternal lineages”, showing clear genetic splits over long distances.

In Namibia and Botswana, populations were genetically similar even when collected 19 to 160 km apart. But in South Africa, worms showed the highest genetic diversity and the strongest differences between sampling sites.

“Strikingly, half of the sampling areas had only one unique genetic ‘fingerprint’ or pattern in their DNA,” Van Asch said. “The fact that these sampling sites all have the same genetic ‘fingerprint’ suggests that the genetic diversity is very low across the Limpopo River Basin to the west of Musina.”

Worms from South Africa’s southernmost sampling areas showed the richest diversity — and may be key to future conservation interventions.

In contrast, Botswana recorded the lowest diversity of all regions, raising concerns about the population’s ability to adapt to environmental pressures. Namibia’s populations appear to have expanded over time, while South Africa and Botswana’s remained stable.

“Nonetheless, the low genetic diversity in mopane worm populations, especially in Botswana, suggests there are fewer variants, which could limit their ability to adapt to environmental changes,” she said.

Van Asch warned that conservation measures — including moving individuals from healthier populations — may soon be necessary.

More urgently, she said, the rapid destruction of mopane woodlands poses an immediate threat.

“A significant portion of harvesting activities remains undocumented. Because mopane worms are harvested widely and without proper controls or monitoring, the practice may have become unsustainable, making the species more vulnerable to extinction.”

Researchers hope to expand the study to Zimbabwe and Zambia, where commercial harvesting is also widespread.

The work forms part of a growing call for formal monitoring systems, better woodland protection and science-based management of one of the region’s most important wild foods.

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