Tricking a wasp into suicide to ensure pollination

At last, the baffling question of how a female fig flower tricks a wasp nearly into suicide to ensure pollination, that has withstood nearly 80 million years of evolution, has been answered in a recent study published in the journal Nature Scientific Reports , by a team of international researchers, including those from the Begaluru-based Indian Institute of Science (IISc). The con game, it seems, starts by mimicking smells, and takes advantage of the symbiotic relation between the tiny fig-wasp and figs.

The wasp lays its eggs in figs, which act like a protective ‘bassinet’ (after the egg hatches, the blind, wingless male wasp burrows a hole, while a female wasp flies out); for the fig, wasps help spread pollen, allowing for seed production.

Edible figs are unisexual, meaning male and female flowers are on different trees. The male fig is perfect for wasps. However, the female fig has long flower stalks and is unsuitable for laying eggs — a female wasp that enters the flower usually dies without burrowing its eggs.

How then is the female fig flower able to attract the wasp and ensure seed production?

Using gas-chromatography and mass spectrometry to analyse the scents of the fig flowers, Renee Borges of the Centre for Ecological Sciences at IISc and her collaborators from China and France have found that the female figs have evolved the strategy of ‘chemical mimicry’, which attracts the wasps who assume it is the scent of the more conducive male fig flower. The symbiotic evolution of the wasp and fig has seen flowers develop unique scents — which are comprised of over 150 volatile organic compounds — to allow the insects to recognise the hosts.

In fig species, where the male and female trees flower at the same time, the researchers found that the female fig closely mimics the scent of the male fig, in an attempt to trick wasps into pollination. However, in fig species where male and female trees flower at different times, the scents were variant — an indication that the female is not pressured into mimicking as ‘desperate’ wasps are likely to choose any available fig.

With the female wasp able to enter only once, entering a female fig flower through clever deceit will end in its purposeless demise.