Researchers Rohit Rohit and Anjali Dhar of the Department of Zoology at Central University of Jammu surveyed six orchard sites spanning 1,073 to 2,302 meters above sea level during the 2025 blooming season. Using a combination of passive pan trapping with ultraviolet-bright blue, yellow, and white bowls and nearly one hundred hours of timed focal observations at flowering trees, they recorded 847 individual floral visitors belonging to 13 species across 10 families and 4 orders. The assemblage included six bee species, four species of hoverflies, and three butterflies, with the western honey bee Apis mellifera, the sweat bee Lasioglossum moroi, the Asiatic honey bee Apis cerana indica, and the drone fly Eristalis tenax together dominating the counts.

The most striking finding is the strength of the relationship between elevation and diversity. Shannon diversity declined in an almost perfectly linear fashion with altitude, with elevation explaining 91.3 percent of the variation in the diversity index. Total abundance fell by 71.8 percent across the gradient, from 238 individuals at the lowest site to just 67 at the highest, while species richness dropped from 13 to 5. The authors caution that elevation and temperature were nearly perfectly collinear in their dataset, with temperatures falling roughly 9.5 degrees Celsius over the 1,229-meter span, so the pattern reflects the composite elevational thermal environment rather than either factor alone. Temporal sampling waves, in which high sites were visited later in the season, add a further phenological confound that the team explicitly acknowledges.

Beneath the aggregate decline lies a pronounced taxonomic reshuffling. Social Apid bees, which made up 39.7 percent of visitors at low elevations, fell to 22.2 percent at high elevations, an absolute decline of 76 percent driven by losses of both honey bee species. Halictidae, represented solely by the sweat bee Lasioglossum moroi, nearly doubled their relative share, rising from 18.1 to 38.2 percent while maintaining near-stable absolute numbers. Hoverflies also held their proportional ground, and the authors attribute this resilience to multivoltine life cycles, larvae that develop in aquatic or aphid-rich habitats decoupled from orchard flowers, and the ability of several species to forage at temperatures as low as 8 to 10 degrees Celsius.

Life-history traits appear to explain much of this filtering. Perennial honey bee colonies demand continuous forage across a long season, conditions that collapse as elevation compresses the bloom window and thins floral diversity. In contrast, Lasioglossum moroi combines flexible sociality with ground nesting, which buffers nests against cold, and can shift to a single generation per year at altitude. Strictly solitary, univoltine bees such as Osmia cornuta and Anthophora confusa vanished from the highest site, consistent with their narrow thermal requirements for emergence. Habitat measurements reinforced the story: bare ground cover, essential nesting substrate for ground-nesting sweat bees, increased with elevation and correlated strongly with L. moroi abundance, while declining non-crop floral richness tracked the disappearance of solitary bees that need diverse forage during their brief adult lives.

At the single site where apple and apricot co-flowered under identical conditions, the team uncovered a clear division of labor. Apid bees accounted for 43.9 percent of apple visits but only 27.1 percent of apricot visits, with both honey bee species showing statistically significant preferences for apple. Hoverflies showed the mirror-image pattern, contributing 42.2 percent of apricot visits against 24.5 percent on apple, with the drone fly Eristalis tenax displaying the strongest crop preference of any species. The generalist sweat bee visited both crops in equal measure. The authors suggest that apple’s larger flowers and higher nectar sugar concentrations suit energy-hungry social bees, while apricot’s nectar volume and volatile profile may better attract olfactory-guided hoverflies, though direct floral trait measurements will be needed to confirm the mechanism.

Behavioral effectiveness scores, combining visit duration with the frequency of stigma contact, pointed to functional complementarity between the two pollinator groups. Honey bees achieved their highest scores on apple, where they contacted stigmas in 78 percent of visits compared with 62 percent on apricot, while all four hoverfly species scored higher on apricot, with E. tenax recording 16.8 versus 10.2 on apple. Overall mean scores were higher on apricot, driven by the extended visits of syrphid flies. The researchers stress these are visitation-based behavioral proxies rather than measured pollen deposition, and confirming actual pollination efficiency would require single-visit pollen assays. Even so, the pattern implies that keeping both crops in the landscape sustains two complementary pollinator guilds.

Network analysis added a structural dimension to the elevational story. High-elevation interaction networks, built from just 8 pollinator and 6 plant species, were more modular and more specialized than their low-elevation counterparts, with modularity rising from 0.38 to 0.46 and network-level specialization from 0.39 to 0.61. Niche overlap among species, measured with Pianka’s index, was significantly lower at high elevations, 0.31 versus 0.58, consistent with intensified resource partitioning when few species share scarce flowers. Within these simplified networks, Lasioglossum moroi emerged as the critical connector, showing the highest degree and species strength and the lowest specialization of any taxon, bridging network modules that would otherwise remain isolated. The authors warn that losing this single species could disproportionately fragment high-altitude pollination webs.

The conservation implications are elevation-specific rather than uniform. At low elevations, the authors recommend wildflower strips to sustain non-crop forage, careful timing of pesticide applications away from peak morning visitation hours, and preservation of dead wood and hollow stems for cavity-nesting solitary bees. At mid-elevations, maintaining a mosaic of both apple and apricot may support transition-zone communities that could serve as refugia under warming. At high elevations, where barely five or six pollinator species persist, priorities include minimizing soil disturbance to protect sweat bee nesting substrate, retaining water features and leaf litter for hoverfly larvae, and ensuring at least one wildflower species blooms throughout the compressed growing season. The strong elevation-diversity relationship also offers a quantitative baseline: repeated surveys at the same six sites could detect the upward range shifts and community disassembly expected as Himalayan winters warm and apple cultivation itself climbs ever higher in search of suitable chill.

Subject of Research: Elevational changes in insect pollinator communities and their interactions with apple and apricot trees in Himalayan orchards

Article Title: Bionomics of insect pollinators and their interaction with host trees in the orchards of Doda, Indian Himalayas

Article References: Rohit, R., & Dhar, A. (2026). Bionomics of insect pollinators and their interaction with host trees in the orchards of Doda, Indian Himalayas. Discover Ecology, 2(1), Article 24. https://doi.org/10.1007/s44396-026-00040-1

Image Credits: AI Generated

DOI: 10.1007/s44396-026-00040-1

Keywords: pollinators, Himalayas, apple orchards, apricot, elevational gradient, bees, hoverflies, plant-pollinator networks, niche overlap, pollinator conservation, Doda, bionomics