Recently, the team led by Professor Huang Shuangquan from the School of Life Sciences at Central China Normal University, along with their collaborators, published their findings online in National Science Review. They discovered that among 41 species of orchids in the Dendrobium genus, 33 orchids have oil-secreting trichomes on their labellum, with these newly discovered oil flowers being pollinated by a specific group of oil-collecting male bees.
Male Euglossine bees collect oil secretions on the labellum of Dendrobium flowers - Image provided by the interviewee
In general, plants that rely on animal pollination typically offer nectar or pollen as a reward for pollinators' efforts. Nectar is a sugary liquid, while pollen is rich in protein, essential for the nutrition of bee larvae.
Fifty years ago, German scientist Stefan Vogel first discovered that some flowering plants are "oil flowers," rewarding pollinators with tiny oil droplets. Oil-collecting female bees use specialized stiff or abdominal hairs to gather flower oils, which are then mixed with pollen as food for their larvae, and also used as nest lining for waterproofing. Worldwide, there are currently known to be around 150 genera in 11 families of oil flowers, with 370 species of oil-collecting bees.
Researchers conducting field studies in Xishuangbanna and Malipo in southern Yunnan, China for six years found that out of 41 species of Orchidaceae and Orchidaceae, 33 orchids belong to the "oil flowers" category. These orchids are mainly utilized by male Euglossine bees, while females prefer visiting oil flowers of Cucurbitaceae to collect oil, nectar, and pollen. They also observed that male Euglossine bees are the sole effective pollinators for 12 species of Dendrobium and one species of Cymbidium orchids.
The first author of the paper, Zhang Meng, a Ph.D. student at Central China Normal University, explained that when placing orchids in experimental populations of oil flowers from the Cucurbitaceae family in the wild, the visitation rate of orchids by oil bees increased hundreds of times. This indicates that the successful pollination of orchids is largely attributed to the co-flowering of Cucurbitaceae oil plants.
It is understood that the Orchidaceae is the second-largest family in the Orchidaceae, with around 1500 species. "Given that the reproductive success of Orchidaceae and other orchids greatly depends on oil bees, maintaining and restoring populations of oil flowers from the Cucurbitaceae family that co-flower in the same area is necessary," said Huang Shuangquan. The multidimensional mutualistic pollination system discovered in this study provides important insights for the conservation of rare resources like orchids: species conservation should follow the concept of a life community.
Professor Hong LIU from Florida International University's Department of Earth and Environment stated, "Many species of Orchidaceae have horticultural and medicinal value, and a deeper understanding of these species will aid in the sustainable utilization and conservation of these valuable biological resources. This research holds significant importance for biodiversity conservation."
For more information on the related paper, visit: https://doi.org/10.1093/nsr/nwae072
