coevolution of bats & flowers

One of the questions in the 2007 90717 paper was on an example of coevolution in bats & flowers. I had a look at the original reference and it's such a neat example, I thought you might be interested in hearing a bit more detail about it.

While we tend to think of insects as the main animal pollinators of flowers, other animals also play a role – birds, bats, even mice. In some cases flower and pollinator have evolved together, sometimes leading to some quite extreme adaptations. Nathan Muchhala (2006) described one example of such coevolution.

Nectar bats are found in the tropical forests of Central and South America, and are responsible for pollintating hundreds of species of plants. Up until now there were no known examples of plants that had specialised for bat pollination (unlike flowers pollinated by insects or birds, which may have quite extreme adaptations eg many orchids). But Muchhala's paper describes one bat, Anoura fistulata, with an exceptionally long tongue – and which is the exclusive pollinator of a flower with an equally long corolla tube (a tube formed from fused petals).

(And how would you measure a bat's tongue anyway? Muchhala did it by keeping them in flight cages & training them to drink sugar-water through modified straws. Have a look at his website for some wonderful images.)

While two related species of bat had tongues of up to 37 and 39mm long, A. fistulata's tongue was 85mm – 150% of its body length, and a relative tongue length greater than in any other mammal. This amazing organ, when not in use, retracts into the chest cavity & is anchored between the heart and the breastbone. The existence of a nectar bat with such a long tongue suggests that it pollinates a flower with an equally long corolla tube, and this is what Muchhala found when he looked at the diets of several Anoura species by identifying pollen from their fur & faeces. A. fistulata was the only bat species to carry pollen from a plant called Centropogon nigricans, which has corolla tubes 8-9cm long. He also found that A. fistulata was the only animal to visit the plant during the study period, suggesting that it is the sole pollinator.


N. Muchhala (2006) Nectar bat stows huge tongue in its ribcage. Nature 444: 701

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