Plants are a lot smarter than we give them credit for. In fact, one tropical plant, the Heliconia tortuosa, chooses which hummingbirds have access to its pollen.
This, in turn, allows the plant to choose those birds that are more likely to spread their seeds farther and with a higher success rate.
Researchers from Oregon State University and the Smithsonian Institution discovered the nature of this particularly picky plant when recently studying it. They noticed that when certain kinds of hummingbirds drank from the plant, the plant responded by allowing its pollen to germinate.
In their experiments, researchers first started by attempting to extract pollen from Heliconia themselves. They had absolutely no luck and wondered why. So they placed the plants in an enclosed area and exposed it to six species of hummingbirds, along with one butterfly. The results were startling: only two specific kinds of hummingbirds, the violet sabrewings and green hermits, consistently fertilized the plants successfully.
What makes these two species of hummingbird so special to Heliconia, though? First, they have longer curved bills that allows them to easily reach the plant's nectar. These two species also travel more than other hummingbirds, meaning that the pollen they carry also travels farther. This also means that these birds collect more pollen, which promotes more genetic diversity, making the Heliconia more competitive among its peers.
What is most striking about this study is that the Heliconia plant seems to understand these things about these two specific types of hummingbirds, using them over other pollinators because of their unique properties to better pollinate the world with its kind.
"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," says Matt Betts, associate professor in the Oregon State University College of Forestry. "If you make a seed or fruit only from distant high-quality pollen, it could be an adaptive advantage."
Betts believes that many tropical plants are highly choosy about their pollinators. However, increasing deforestation and human encroachment upon those plants' territories could still result in these plants becoming extinct. More areas of the rainforest have been broken up for farming, so it's important to still maintain "corridors" between areas populated with these plants.
"We need to be more careful in how we manage landscapes in order to maintain the movements and occurrence of these key species," says Betts. "We know that if we make corridors to connect patches, if we have bigger patches of tropical forests, those species will be maintained, and this plant and its pollinators will do a lot better."
