Are olfactory signals sufficient to attract fig pollinators?
1998
Gibernau, Marc | HossaertMcKEY, Martine | Frey, Jürg | Kjellberg, Finn
Flower fragrances are important stimuli in attracting insect pollinators. Different odours attract different pollinators and can, in some cases, achieve specific relationships. Among highly specific pollination systems, the genus Ficus (Moraceae) represents one extreme example, as each Ficus is pollinated by its specific wasp species. The identification of a receptive fig occurs in two steps and chemical information appears to be important in both stages. First, all figs of a tree develop synchronously, so that when the wasps emerge, their natal tree only bears mature figs. Therefore the wasps must locate another tree, bearing receptive figs. This long-distance attraction suggests olfactory signals. Second, once on the fig, fig wasps explore its surface by tapping their antennae on the surface (antennating) as they walk over it. This behaviour suggests contact chemostimulation. The fragrance of receptive Ficus carica figs was extracted using pentane, and the extracts tested on its pollinator wasp (Blastophaga psenes). The results from both distance attraction and contact stimulation experiments indicate that chemical compounds are sufficient to mediate these two steps. Visual cues are not sufficient to attract and stimulate fig pollinators and are probably only minor stimuli compared to the chemical signature of the fig. In this way, Ficus pollination is strikingly different from other specific pollination systems such as Trollius and Yucca, where visual cues are important in attraction to flowers.
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