Deep in the tropical forests of Central and South America, a tiny bird with iridescent feathers has quietly become one of nature's most powerful engines for creating new plant species. Scientists at the University of Reading in the United Kingdom have discovered that hummingbirds make bromeliad plants — the family that includes pineapples — evolve into new species at twice the rate of plants pollinated by bees, bats or moths.
The research team studied 403 types of bromeliad, a plant group with over 3,700 species ranging from tiny air plants perched on tree branches to the familiar pineapple grown on farms worldwide. They found that three out of every four bromeliad species are visited by hummingbirds, which drink the sweet nectar inside each flower. As the birds move from bloom to bloom, pollen sticks to their beaks and feathers, fertilizing the next plant they visit. Over millions of years, many bromeliad flowers have actually changed shape and color to better attract their feathered partners.
Where hummingbirds do the work, new species appear at a rate of 2.77 per million years — compared to just 1.46 for plants relying on other pollinators. Elizabeth Forward, a PhD researcher at the University of Reading who led the study, said bees and wasps were the original pollinators of bromeliads, but hummingbirds joined later — and not just once. "Time and again, different branches of the family swapped one pollinator for another, and that swapping is still going on today," she explained.
Dr. Jamie Thompson, a senior researcher at the university, said hummingbirds feed high in mountain forests where plants grow in scattered patches separated by valleys and peaks. "Cut off from their neighbors, those groups drift apart over time until they become species in their own right," he said. The researchers note that this rapid speciation is remarkably recent — much of this diversity arose within just the past 20 million years, a tiny blip on evolutionary timescales.
But this close partnership now faces risks. Many bromeliads grow in mountain forests threatened by farming and climate change, and 81% are potentially at risk of extinction. One in ten hummingbird species is also at risk of disappearing, and six in ten are declining in number. If a hummingbird species vanishes, the plants that depend on it could vanish too.
The good news: about one in six bromeliad species accepts more than one type of pollinator, which could give them a safety net if their primary partner struggles. Scientists say the detailed pollinator records from this study give researchers a valuable foundation for protecting both the plants and the birds that help create such remarkable diversity.