Fig Wasps & Fig Trees

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Figs need to be pollinated by wasps in order to continue to procreate.

Fig wasps and fig trees have an incredible symbiotic relationship. Each species needs its counterpart to survive. The trees depend on the wasps for pollination and the wasps depend on the tree for hatching eggs and breeding. This relationship has evolved over millions of years.

  1. Mutualism

    • Fig trees and fig wasps are completely dependent on one another for survival, a classic case of mutualism. Fig trees do not have any observable, external flowers to aid with pollination. Instead, they need to be pollinated by fig wasps, a miniature wasp that is just a few millimeters long. In turn, a fig wasp needs a fig tree, and specifically its figs, in order to survive. It is there that they lay eggs, are born and mate.

    Types

    • There are more than 700 types of fig trees and fig wasps, although many of the species of fig wasps have not yet been extensively studied. In most cases there is a specific species of wasp for each species of tree, but occasionally this mono-relationship does not hold. Despite the large number of species, just two are native to the United States. The Florida strangler fig (Ficus aurea) and the shortleaf fig or wild banyan tree (Ficus citrifolia) are native to the United States. Their associated wasp species are the Pegoscapus mexicanus and the Pegoscapus tonduzi.

    Pollination

    • Female fig wasps are the only ones that fly and move from tree to tree. After breeding, a female fig wasp goes in search of another fig tree of the same species. Upon locating a suitable tree, the wasp squeezes into the fig through a tiny opening at one end, called the ostiole. This is a very tight fit and sometimes she loses her antennas or wings along the way. Upon arriving in the center of the fig she pollinates the stigmas with the pollen she has carried from the fig in which she was born and mated, allowing the fig tree to continue its life cycle.

    Wasp Life Cycle

    • When the female fig wasp enters a fig and pollinates it, she also lays her eggs. These eggs will grow and hatch in the fig. Males are born wingless and never leave the fig. Instead, they mate with the females and then chew holes in the fig walls so that the females can fly away before dying inside the fig. The females become covered in pollen or load up special pockets with pollen and leave in search of another tree, repeating the life cycle of the fig wasp.

    Retaliation and Response

    • The fig tree and fig wasp relationship depends on mutualism, but occasionally this mutualism falters. There are two ways for a female fig wasp to carry pollen with her: some species use a passive method where the female becomes covered when leaving the previous fig, and some species use an active method in which a female must physically load herself up with pollen in special pollen pockets before departing. In the first situation, the mutualism nearly always works correctly. However, with the second method, sometimes the female wasps grow lazy and do not load up with pollen. Instead they simply head to another tree and lay their eggs without ever pollinating the tree. However, nature has built in a defense. If the tree has a fig that has not been pollinated but is being used as a hatching ground, it will release the fig, letting it fall to the ground, and thereby killing the eggs and wasps inside of it. These sanctions enforce the symbiotic relationship.

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References

  • Photo Credit Figs image by Freeze Frame Photography from Fotolia.com

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