Fig Trees Retaliate Against Cheating Wasps

Over 700 paired species of fig trees and wasps have symbiotic relationships. The fig tree host wasp eggs, and the wasps pollinate the fig trees in return. But according to a new study, if the wasps don't pollinate the host plants, the fig trees retaliate:

If the wasps don't do their duty, the trees respond by enacting a sanction — aborting their fruit, killing off the teeming mass of baby wasps. A new study of this killer tree phenomenon, published in Proceedings of the Royal Society B comes from Cornell University and The Smithsonian Tropical Research Institute, shows that negative reinforcement may be an important part of symbiotic relationships.

Pollination by wasp comes in two varieties: passive and active. With passive pollination the wasps carry pollen that happens to stick to their bodies; where with active pollination they collect pollen in special pouches to deliver to the flowers.

With the passive pairings, the fig trees abort their fruit far less often than with active pairs. In the actively pollinating groups, the tree species that tend to enforce sanctions less often have a higher occurrence of freeloader wasps, who take advantage of the figs without doing any of the work. Inversely, by using the sanction option more frequently, some fig species have a lower incidence of non-pollinating insects.

Link | Scientific Paper | Photo: University of British Columbia