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Pollinators of fig trees

(Life; Embryophyta (plants); Angiospermae (flowering plants); Eudicotyledons; Order: Rosales; Family: Moraceae; Genus: Ficus)

Interaction of figs and fig wasps

Consideration of how fig trees are pollinated may leave the observer with a conundrum. Pollinators of plants can often be predicted, based on flower characteristics of colour, fragrance and shape. For example, white, fragrant flowers with a long corolla tube are usually pollinated by Hawk moths, which are nocturnal and have a long tongue. Fig trees are unique in that the flowers are completely concealed within the fig, an enclosed inflorescence, with the hundreds of tiny florets lining the inside of a central cavity. Attempting to guess who pollinates figs and how the act is carried out would no doubt lead to the conclusion that the pollinator, as for many plant species, must be highly specialized. Careful, close and patient observation of figs that are receptive for pollination would enlighten the observer to a fascinating world, for fig trees are completely dependant on tiny wasps, a couple of millimeters long, for their propagation and survival. These fig wasps are the sole pollinators of fig trees and in turn, fig wasps can breed nowhere else but inside figs, a relationship that is a classic example of an obligate mutualism (neither party can survive without the other) that has evolved over the last 60 or so million years.

Fig_wasps_emerging_from_Ficus_sur Fig wasps emerging from the fig of Ficus sur they have bred in.
Ceratosolen_capensis_on_finger Ceratosolen capensis the pollinator of Ficus sur on a finger to illustrate the small size of fig wasps.
Ceratosolen_capensis_emerging_from_gall Ceratosolen capensis emerging from her gall inside a fig of Ficus sur.

Each fig tree species is usually pollinated by one fig wasp species that is only associated with that fig species, a host-specific relationship that plays a major role in the prevention of hybridisation between different species of fig trees. However, only 300 of a potential 750 fig wasp pollinator species are currently known (there are 750 species of Ficus in the world), and already we know that the one-to-one rule between fig tree and wasp does not always hold, so the interaction is not as well defined as initially appears. What the exceptions do tell us, however, is that we are dealing with a continually evolving dynamic system, the intricacies of which we are only just beginning to understand.  

Courtella_wardi_ovipositing

How fig trees are pollinated

Credits

Illustrations and photographs Simon van Noort (Iziko Museums)

Web authors Simon van Noort (Iziko South African Museum)

and Jean-Yves Rasplus (INRA, France)

Copyright 2004-2013 Iziko Museums of South Africa

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