When leaves act like flowers: how dwarf palms attract their pollinators

In pollination mutualisms, floral odours are signals advertising the presence and location of rewards. However, in the case of the dwarf palm (Chamaerops humilis) and its species‐specific pollinating weevil (Derelomus chamaeropsis), rewards and advertisements are spatially separated. Flowers provide their specific pollinators with food and sites for both egg laying and larval development, but do not advertise them with floral odours or visually conspicuous petals. Insect behavioural bioassays revealed that pollinators are attracted by scents emitted by the leaves, which provide no rewards. These scents are released by large structures located at the sinuses of the palmate leaf. Such scent‐releasing structures have not been previously reported on palm leaves, and we suggest that they may represent an ‘exaptation’ (pre‐existing trait that acquired new functions). We also propose that such functional crossovers between vegetative and reproductive domains may be more frequent in plants than is currently documented.