How Tropical Plants Pick the Best Hummingbirds to Pollinate Their Flowers

Tropical flowers may actually pick and choose the best pollinators rather than waiting patiently for one. Scientists have found that some plants are able to recognize the best suitors and "turn on" to increase the chance of success.

The new findings come after researchers discovered that the showy red and yellow blooms of Heliconia tortuosa, an exotic tropical plant, recognize certain hummingbirds by the way the birds sip the flowers' nectar. The plants respond by allowing pollen to germinate, ultimately increasing the chances for successful seed formation.

In order to investigate this phenomenon a bit further, the scientists tried to pollinate the Heliconia plants by hand. Yet the researchers were unable to do so successfully. Then, the scientists exposed the plants to six species of hummingbirds and a butterfly. In the end, two species of hummingbirds achieved more than 80 percent success in fertilizing the plants, while the others didn't have nearly as much success.

"The ones that turned in on tended to have long curved bills that could reach the nectar," said Matt Betts, one of the researchers, in a news release. "The ones that couldn't turn it on had shorter bills and couldn't get as much nectar.

The scientists modified their hand pollinating methods to mimic the birds extracting nectar and were able to achieve similar success in fertilizing plants. The researchers found that the two species that the flowers preferred also ranged more widely.

"The mechanism may have evolved to enable the plant to sort out pollinators that are likely to be carrying high-quality pollen from those carrying poor-quality pollen," said Betts. "It's a big energy savings. If you bother to make a seed and fruit every time you get pollen, that's a lot of energy expenditure; you could be making a seed from your siblings' genes. If you make a seed or fruit only from distant high-quality pollen, it could be an adaptive advantage."

The findings reveal that it's important to know how plants react to pollinators since this could be crucial for managing landscapes, especially where key species are involved.

The findings are published in the Proceedings of the National Academy of Sciences.

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