DOI: 10.1002/ppp3.70297 ISSN: 2572-2611

Female Melanostoma hoverflies pollinate Cypripedium yatabeanum through a Paphi

Kenji Suetsugu, Yudai Okuyama
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Societal Impact Statement

Conserving rare plants requires understanding the ecological interactions that enable their reproduction. Most studied Cypripedium species are pollinated by bees, but the pollinators of many slipper orchids remain undocumented. We show that Cypripedium yatabeanum is pollinated by female aphidophagous hoverflies despite sharing broadly similar floral architecture with the closely related, bee‐pollinated Cypripedium guttatum . This contrast indicates that pollinators cannot be inferred from floral structure alone. Conservation strategies should therefore protect not only orchid populations but also their pollinators and the surrounding resources that sustain them, including flowering plants for adults and aphid‐rich habitats for larvae.

Summary

A deceptive flower must attract visitors and guide them into contact with its reproductive organs. This mechanical control is most pronounced in slipper orchids, whose pouch‐like labella trap insects and force them out through narrow basal apertures. Although most studied Cypripedium species are bee‐pollinated, fly pollination has been reported repeatedly.

We investigated the previously undocumented pollination biology of Cypripedium yatabeanum , a member of section Bifolia with a pitcher‐shaped labellum, broad dorsal opening, glossy rim, and downward‐curved, ridged staminode. This architecture resembles that of the closely related, bee‐pollinated Cypripedium guttatum and several hoverfly‐pollinated Paphiopedilum species.

Female Melanostoma interruptum and Melanostoma mellinum were legitimate pollinators. They hovered around flowers, landed on the staminode or adjacent glossy surfaces, and often slipped from the staminode into the pouch. Trapped flies escaped through basal apertures, contacting the stigma before acquiring a sticky pollen mass from an anther. A larger fly entered but could not escape, consistent with size‐dependent mechanical filtering. Exploratory scent analysis identified β‐myrcene, geraniol, and  p ‐cresol as the main volatiles in the DVB/CAR/PDMS profile. A PDMS fiber also detected a trace of ( E )‐β‐farnesene.

Cypripedium yatabeanum is therefore pollinated by female Melanostoma hoverflies through a Paphiopedilum ‐like trap. Its yellowish‐green display, prominent staminode, and glossy surfaces suggest anther/pollen and nectar mimicry, with volatiles as candidate supplementary signals. Comparison with bee‐pollinated C. guttatum shows that broadly similar trap architecture can accommodate different pollinator guilds, with divergence in attraction signals as a possible explanation.

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