Plant Uses 'Private Password' Scent for Single Pollinator
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- Suetsugu Kenji of Kobe University led a study in Current Biology (2026, DOI: 10.1016/j.cub.2026.03.002) decoding how the climbing plant Smilax insularis uses a rare scent to guide its pollinator to male flowers first and female flowers later.
- Dihydroedulan I — a compound not previously identified as the dominant floral scent component in any plant — was the main chemical signal, attracting only the gall midge Dasineura heterosmilacicola in field tests; no other insects responded, and even slight molecular twists failed to draw the midge.
- Male and female flowers release the same chemical at different times of day: male flowers in the early morning, female flowers from late morning until around noon — a temporal offset that promotes reliable pollen transfer.
- The partnership is an obligate brood-site pollination mutualism: the midge lays eggs in male flowers, where larvae feed on surplus pollen, then carries pollen to female flowers, where eggs are rarely laid — keeping both the plant and the insect in the arrangement.
- Suetsugu called the chemical a "private chemical password" and said he now wants to study how Smilax produces a scent so dominated by a single compound, noting that the molecule may originally have functioned as an insect repellent before being repurposed as an exclusive attractant.
Why it matters: The study provides rare field-level evidence for the long-hypothesized 'private channel' in obligate brood-site pollination mutualisms, showing that one compound can govern a species-specific partnership. Suetsugu's own note that dihydroedulan I may have originally evolved as a repellent — not an attractant — reframes the evolutionary question: how does a single molecule get repurposed into an exclusive chemical language?
