Study uncovers hidden bee diversity across Arunachal Pradesh 

Guwahati: The forests and mountains of Northeast India are home to a remarkable and largely unexplored world of bees, according to a new study that has mapped pollinator diversity across one of the planet’s most biologically rich regions.

Led by Nyabin Riso, Chihi Umbrey and Hiren Gogoi of Rajiv Gandhi University, Arunachal Pradesh, the four-year study recorded 63 bee species belonging to five families across Arunachal Pradesh, Nagaland and parts of Assam, revealing that the Eastern Himalaya may harbour far more pollinator diversity than previously known.

Published in the International Journal of Tropical Insect Science, the research represents one of the most comprehensive assessments of bee distribution ever conducted in Northeast India.

The findings are significant because Northeast India sits at the crossroads of two global biodiversity hotspots—the Himalaya and Indo-Burma regions—yet remains one of the least-studied areas in the world for bee diversity.

Scientists say the region’s rugged terrain and vast elevational range have left major gaps in understanding how pollinators are distributed across the landscape.

To fill that gap, researchers surveyed 286 transects between 2018 and 2021, covering habitats ranging from tropical lowlands at just 78 metres above sea level to alpine landscapes soaring above 4,266 metres. Along the way, they collected and identified more than 1,000 bees, including honey bees, bumble bees, stingless bees, carpenter bees and solitary bees.

What emerged was a striking picture of mountain-driven biodiversity.

The study found that altitude was the single most important factor influencing bee distribution. 

Researchers documented a sharp ecological divide at the 1,000-metre mark: 24 species were found exclusively below 1,000 metres, while another 24 occurred only above that elevation. Just 15 species were shared between the two zones.

Far from becoming poorer in species as conditions grew colder and harsher, the mountains proved to be unexpectedly rich. Statistical analyses showed that sites above 1,000 metres supported greater bee diversity and a more even distribution of species than lower-elevation habitats.

The findings suggest that the Eastern Himalaya’s higher reaches may serve as important refuges for pollinators, particularly at a time when bee populations worldwide are facing increasing pressure from habitat loss, pesticide use and climate change.

Bees are widely regarded as bioindicators of ecosystem health because they respond quickly to environmental disturbances.

Among the most iconic species recorded was the giant Himalayan honey bee, Apis laboriosa, a cliff-nesting bee renowned for its ability to survive in some of the world’s most challenging mountain environments. The study found that the species became increasingly abundant at higher elevations, reinforcing its reputation as a specialist of high-elevation ecosystems.

Bumble bees showed a similar pattern. Ten of the 13 bumble bee species documented were found only above 1,000 metres, with species such as Bombus luteipes and Bombus prshewalskyi displaying strong positive relationships with altitude.

Their ability to generate body heat allows them to thrive in the cool conditions of alpine forests and meadows where many other insects struggle to survive.

The study also revealed how different habitats support different pollinator communities. Alpine forests and meadows emerged as strongholds for bumble bees and several solitary bee species, while bamboo forests supported stingless bees such as Lepidotrigona arcifera and Tetragonula iridipennis.

The findings underscore the importance of habitat diversity in maintaining healthy pollinator populations.

Not all species were widespread. More than one-third of the recorded bees—23 species in total—were found at only a single location, suggesting that many may occupy highly specialised ecological niches and could be vulnerable to environmental change.

At the other end of the spectrum was the Asian honey bee, Apis cerana, which emerged as the region’s most successful and widespread pollinator.

It was recorded in 38 of the surveyed grid cells and had the highest population density among all species documented during the study.

Perhaps the most intriguing finding is that scientists believe they have not yet discovered the full extent of the region’s bee diversity. Statistical models showed that species accumulation curves above 1,000 metres had not fully levelled off, indicating that additional species are likely to be found with further surveys.

In other words, some of Northeast India’s bees may still be waiting to be discovered.

“The study showed unique altitude-based distribution patterns for different species, and wide variation in altitude may shape the rich diversity of bees in the region,” the authors noted.

For scientists, the message is clear: the mountains of the Eastern Himalaya are not just scenic landscapes. They are living reservoirs of pollinator diversity, and protecting them may be crucial for safeguarding some of Asia’s most important—and least understood—bee populations.

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