Understanding how diverse species manage to coexist in the same community, particularly when competing for similar resources, remains a fascinating puzzle in ecology. Bumblebees, key pollinators in the Northern Hemisphere, depend almost entirely on floral rewards to sustain their life cycles. This dependence underscores not just their ecological significance, but also their vital role in natural and agricultural ecosystems. China is recognized as a global diversity hotspot for bumblebee species.

In the Hengduan Mountains of eastern Himalayan in southwest China, it is quite common to observe more than a dozen bumblebee species coexisting with remarkable abundance within a same community. Unraveling how they navigate the challenge of avoiding excessive competition while utilizing the same floral resources to achieve stable coexistence is an outstanding and unresolved scientific dilemma.

Focusing on the floral resource partitioning among the coexisting bumblebees, the Plant Reproductive Ecology Group at Wuhan Botanical Garden of the Chinese Academy of Sciences conducted a five-year field experiment in an alpine meadows of the Hengduan Mountains. This research documented interactions among 13 bumblebee species and nearly 120 plant species, recording 10,598 connections. Simultaneously, floral traits and bumblebee characteristics were measured.

The study offered an in-depth exploration of the principles governing their use of floral resources, analyzed across three distinct levels: species, colony, and individual. It was found that bumblebees' utilization of floral resources exhibited significant dynamism over the years, yet demonstrated clear modularity at both species and colony levels, indicating differentiated strategies for exploiting floral resources. The primary factors influencing the choice of floral resources among species were attractive characteristics such as the color and shape of the flowers, with variability at the individual level also significantly impacting bumblebees' selection of floral resources. Despite bumblebees displaying evident strategies to avoid competition in the use of floral resources, the flexibility in their utilization strategies was remarkably higher than expected.

This research enhances scientific understanding of the mechanisms sustaining bumblebee diversity, providing a scientific foundation for the conservation of this important strategic resource.

This study was published on Ecology, titled "Floral resource partitioning of coexisting bumble bees: Distinguishing species-, colony-, and individual-level effects". Associate Professor YE Zhongming is the first author, Prof. YANG Chunfeng is the corresponding authors. This research was supported by the National Natural Science Foundation of China.

The pattern of bumblebees' partitioning use of floral resources on the species level (Image by WBG)