Wildlife TV

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Mutualism: The intimate relationship between fig trees and fig wasps

on May 16, 2013

The concept of ‘symbiosis’ in the natural world may be familiar to many people but it’s not always as simple as two organisms living together in mutually beneficial relationships; the term actually refers more broadly to close relationships between living things, whether beneficial for both parties or not; for example, a parasite such as a tick has a symbiotic relationship with a buffalo even though the buffalo gains nothing from the interaction.

Sometimes animals live alongside each other and form relationships that are mutually beneficial, or indeed required for each other’s survival; this is called (appropriately) ‘mutualism’ and there are numerous examples all over the world. There is one remarkable example in the African bush that would go unnoticed if it weren’t for scientific investigation; this is the relationship between the fig wasps (from the family Agaonidae) and the fig trees (from the genus Ficus); without each other, neither species would survive.

A tiny fig wasp sitting on a fig fruit.

A tiny fig wasp sitting on a fig fruit.
Picture credit.

The female fig wasp, once she’s found a host tree, squeezes through a tiny hole in one of the fruits where she will spend the rest of her life; she lays her eggs and dies, however, she carried the pollen of another fig tree with her and pollinates the new tree by brushing up against the flowers inside the fig fruit. But where did the pollen come from you ask? We’ll get to that. After the fig has been pollinated though, it hardens and encapsulates all the eggs safely inside.

The eggs develop and the larvae hatch inside the fig fruit, feeding from the flesh inside, but it is the males who mature first and mate within the fruit (fortunately, enough wasps will have laid their eggs inside the fruit that the males won’t be exclusively mating with their sisters (accidents happen though)). These poor male wasps don’t have much of a life; after mating they dig a hole through the fruit and then fall to the ground to die, having lived their whole lives squirming around inside a dark chamber. But with their last action, they have provided an escape route for the females who, once matured, will leave the fruit and fly away, covered with the pollen of their nursery fig and already laden with fertilised eggs. The females fly away and waste no time; they go in search of another fig tree that they can pollinate and lay their eggs in, and the cycle starts all over again.

Sofia sits on a fig tree, sharing it with the fig wasps that call it home.

Sofia sits on a fig tree, sharing it with the fig wasps that call it home.

As you can see, the lives of these two organisms are intimately intertwined; the wasps spend almost the entirety of their lives within the fig fruits, keeping them safe and providing them with food and the fig tree gets to employ a guaranteed pollinator that allows it to reproduce. The natural world is full of such wonders and the more we investigate the more we’ll discover.

Much love,

-Nick

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3 responses to “Mutualism: The intimate relationship between fig trees and fig wasps

  1. Peter Charles says:

    My fig trees have irises (or something similar) growing at the base. This happens even with planted fig cuttings. Is there a special relationship between the two?

    • Wildlife TV says:

      I couldn’t say anything conclusively but maybe there could be external causes for a relationship between those two plants, for example; a bird species might enjoy feeding on the seeds of the irises as well as the fig fruits and so brings the two together when feeding on one and defecating out the seeds of the other at the same site. I’m just speculating though, I don’t know about the specific situation you’re describing, but in the wild there are sites known as ‘nutrient hotspots’ where clusters of plant life grow in small communities, often around an established tree where birds perch and drop seeds in their faeces.
      Cheers,
      -Nick

      • Peter Charles says:

        Thanks Nick. That does seem likely. I will plant the next cutting with a ground cover to prevent another growth and see the result. Once again, thanks.

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