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Bonded for ever with coevolution

Read time: 2 mins

What do sword billed humming birds, fig wasps and acacia ants have in common? It’s the phenomenon of co-evolution, where these organisms are dependent on other organisms for survival and they reciprocally affect the other’s evolution.

The sword billed humming bird (Ensifera ensifera) has a very long bill measuring upto 10 centimeters, almost as long as the rest of its body! Due to its long bill, preening is nearly impossible and the bird must clean itself with a good-old scratch. What does the bird get in return for the poor hygiene that might affect its health and flying with the energy consuming “sword”? The sweet nectar of the flower Passiflora mixta! This flower has a 7 to 15 cm long tube at the bottom of which it offers nectar which can be reached only by the sword billed humming bird, making it the only pollinator for the plant. Having such a specialised pollinator ensures that none of the sex cells produced by the plant reach any other species than its own. This relationship makes the plant and the bird dependant on each other for their survival and evolve with each other.

Many flowering plants also show instances of coevolution to entice pollinators. Since insects can see in the ultraviolet (UV) range unlike us, flowers have bull’s eye patterns or leading lines like runways, which guide the pollinators to where the nectar is. In the process of sucking the nectar, the pollinators get doused in the pollen of the plant, which is then delivered to another flower. Plants use the pollinator’s mobility to find a mate, by offering it a small energy rich bribe of nectar.

Though coevolution is mesmerising, there is an obvious downfall - the extinction of one of the partners will eventually lead to the extinction of the other, making it important for conservation efforts to look at ecosystems as a whole, rather than individual organisms.