Hummingbirds seem to act like an engine for new species
In the fragmented mountain landscapes of Central and South America, hummingbirds and bromeliads have spent millions of years shaping one another — a partnership so generative that it doubles the pace at which new plant species emerge. Researchers at the University of Reading have now quantified this co-evolutionary force, finding that hummingbird pollination drives bromeliad speciation at nearly twice the rate of any other pollinator. What took nature millions of years to build, however, now faces rapid unraveling: habitat loss and climate change threaten both partners, and the very intimacy that accelerated diversity may hasten its collapse.
- Hummingbirds are not merely pollinators — they are evolutionary engines, pushing bromeliads to form new species at 2.77 per million years, nearly double the rate driven by bees, bats, or moths.
- The mountain geography of the Americas amplifies this effect, isolating plant populations in scattered highland patches where genetic drift quietly transforms one species into many.
- The partnership is now fracturing under pressure: 81% of bromeliads face possible extinction, one in ten hummingbird species is threatened, and six in ten are already in decline.
- Because most bromeliads depend exclusively on a single hummingbird species, the disappearance of one bird could trigger a cascade of plant extinctions — turning co-evolution's gift into a vulnerability.
- A small fraction of bromeliads — roughly one in six — accept multiple pollinators, offering a model of resilience that conservationists may need to understand urgently.
- The University of Reading's new species database now stands as both a scientific foundation and a quiet warning: a record of interdependence compiled at the moment it is most at risk.
In the mountain valleys of Central and South America, hummingbirds and bromeliads have been reshaping each other for millions of years. Researchers at the University of Reading have now measured the scale of that influence: where hummingbirds pollinate, new bromeliad species emerge at 2.77 per million years — nearly double the 1.46 rate seen with bees, bats, or moths. The finding, drawn from a survey of 403 bromeliad species, was published this week in the Botanical Journal of the Linnean Society.
Lead researcher Elizabeth Forward explained that bees and wasps were bromeliads' original pollinators, but hummingbirds arrived later and have been displacing them repeatedly across different plant lineages — a process still unfolding today. The acceleration is partly geographic: hummingbirds feed in high mountain terrain, where plant populations grow in isolated patches separated by valleys and peaks. Cut off from one another, these populations drift genetically until they become distinct species. The mountains themselves function as a machine for biological diversity.
Bromeliads span a remarkable range — from the familiar pineapple to air plants found in millions of homes — but most are small, perching on branches or rocks, their leaf rosettes collecting water and sheltering frogs and insects. Over millions of years, their flowers have evolved in color and form to attract hummingbirds, which carry pollen from bloom to bloom on their feathers.
That intimate partnership now faces collapse from both ends. Eighty-one percent of bromeliads are considered possibly at risk of extinction, while one in ten hummingbird species is threatened and six in ten are declining. For the majority of bromeliads, the relationship with a single hummingbird species is exclusive — meaning the loss of one bird could erase the plants that depend on it entirely.
About one in six bromeliads studied accept more than one type of pollinator, a redundancy that may offer some protection. But for most, the bond remains fragile. The research team's database now documents which plants rely on which birds at the very moment both are under unprecedented pressure — a record that may yet determine what can be saved.
In the mountains of Central and South America, where valleys carve the landscape into isolated pockets, a quiet evolutionary race has been unfolding for millions of years. Hummingbirds and bromeliads—the plant family that includes pineapples, air plants, and thousands of smaller relatives—have been locked in a partnership so tight that it has reshaped both species. Now, researchers at the University of Reading have measured just how powerful that partnership is: hummingbirds drive bromeliad evolution at twice the speed of any other pollinator.
The finding emerged from a comprehensive survey of 403 bromeliad species and the animals that pollinate them. The numbers are striking. Three out of every four bromeliads studied are visited by hummingbirds. And where hummingbirds do the pollinating work, new plant species emerge at a rate of 2.77 per million years—nearly double the 1.46 rate seen in plants pollinated by bees, bats, or moths. The research, published this week in the Botanical Journal of the Linnean Society, suggests that hummingbirds function as an evolutionary accelerant, pushing bromeliads toward speciation faster than any other force in the system.
Elizabeth Forward, the lead researcher, explained the mechanism. Bees and wasps were the original pollinators of bromeliads, she noted, but hummingbirds arrived later and began displacing them—not once, but repeatedly across different plant lineages, a process still happening today. What makes this acceleration possible is geography. Hummingbirds feed in the high mountains, where plants grow in small, scattered patches separated by deep valleys and steep peaks. These isolated populations, cut off from one another, drift genetically over time until they become distinct species. The mountains themselves become a engine for diversity.
The bromeliad family spans an enormous range of forms. Pineapples are the outliers—they grow in soil and produce the large, familiar fruit—but they share the same basic blueprint as their relatives: strappy leaves, a flower spike, and a dependence on hummingbirds for reproduction. Most other bromeliads are smaller, perching on tree branches or rocks, many of them forming water-filled leaf rosettes that function as tiny ecosystems, hosting frogs and insects. Air plants, now found in millions of homes worldwide, are also bromeliads. All of them have been shaped by hummingbird visitation. Over millions of years, their flowers have evolved in color and shape to attract and accommodate their avian pollinators. The birds drink the nectar, pollen clings to their feathers, and the cycle continues at the next bloom.
But this intimate co-evolution now carries profound risk. The mountain forests where these plants grow are being cleared for agriculture and degraded by climate change. Eighty-one percent of bromeliads are considered possibly at risk of extinction. At the same time, one in ten hummingbird species faces extinction, and six in ten are declining in number. The partnership that accelerated diversity now threatens to collapse it. If a hummingbird species disappears, the bromeliads that depend solely on it may vanish too. The very mechanism that drove speciation could become a liability.
Some bromeliads have hedged their bets. About one in six of the plants studied accept pollination from more than one type of animal—bees alongside hummingbirds, or bats, or moths. This redundancy may offer a buffer against the loss of any single pollinator. But for the majority, the relationship remains exclusive and fragile. The research team's database now stands as a foundation for future study, a record of which plants depend on which birds at a moment when both are under unprecedented pressure. The question facing conservation is whether that record will become a chronicle of what was lost.
Notable Quotes
Hummingbirds seem to act like an engine for new species. They feed high in the mountains, where plants grow in small patches split apart by valleys and peaks.— Dr. Jamie Thompson, University of Reading
Bees and wasps were the first to pollinate bromeliads, but hummingbirds muscled in later, and not just once. Time and again, different branches of the family swapped one pollinator for another.— Elizabeth Forward, lead researcher
The Hearth Conversation Another angle on the story
Why does geography matter so much here? Why do mountains specifically speed up evolution?
Because mountains isolate populations. A hummingbird-pollinated plant on one peak can't easily reach another peak across a valley. Over time, those separated groups accumulate different mutations, different traits. They become strangers to each other. Eventually they can't interbreed anymore. That's speciation. Lowlands don't have that barrier effect—pollinators move freely, genes flow between populations, everything stays mixed.
So hummingbirds aren't actually causing faster evolution. The mountains are.
Both. The mountains create the isolation, but hummingbirds are the ones feeding in those mountains, visiting those scattered plants. Bees and bats and moths don't climb as high or range as widely. Hummingbirds do. They're the ones connecting—or failing to connect—those isolated patches.
The study mentions that hummingbirds "muscled in" on bromeliads. What does that mean exactly?
Bromeliads were originally pollinated by bees and wasps. But at some point, hummingbirds started visiting them too. And over evolutionary time, some bromeliad lineages shifted their entire pollination strategy toward hummingbirds. It happened multiple times, independently. That's the muscling in—hummingbirds didn't invent the relationship, they invaded it and became dominant.
If 81 percent of bromeliads face extinction, why isn't this a bigger crisis?
It might be. But bromeliads aren't charismatic. They're not pandas or elephants. Most people don't know what they are. And the crisis is slow—it's habitat loss and climate change, not a sudden event. Those are harder to mobilize around. But yes, if you lose a hummingbird species in a mountain range, you could lose every bromeliad that depends on it.
The ones that accept multiple pollinators—are they thriving?
The study doesn't say. It just notes they exist and might have better odds. But we don't know if they're actually surviving better or just hedging their bets without it mattering yet.