Why some Hibiscus flowers lost their bullseye patterns

Flowers captivate us with their colors, but nature often hides its most remarkable stories in what we overlook. Among Hibiscus blossoms, the bullseye pattern is a bold circle of pigment near the petal base.

It draws pollinators like bees, making it seem indispensable. Yet in a surprising twist, many Hibiscus species have evolved to lose this feature. Why would evolution erase something so useful?

New research by scientists at the Sainsbury Laboratory, University of Cambridge, explores this very question. Their findings reveal a deep genetic mystery and a powerful reminder that what benefits one part of life’s puzzle may constrain another.

Beneath the surface of every petal lies a story of choices shaped by genetics, the environment, and the tug-of-war between function and cost.

Bees love bold petal spots

The iconic bullseye pattern on Hibiscus petals serves more than aesthetic appeal. It functions as a visual cue that guides pollinators – particularly bumblebees – toward the reproductive heart of the flower.

These dark spots are rich in anthocyanins, a group of pigments that reflect less ultraviolet light and enhance contrast for bee vision.

“We found that bumblebees clearly prefer flowers with large, dark bullseyes, which act as visual guides directing them to the flower’s centre,” said May Yeo, first author and PhD student in Dr. Edwige Moyroud’s group.

This preference should, in theory, drive the evolution of increasingly bold patterns across generations.

Yet researchers noticed an odd trend. Despite the pollinators’ clear bias, some species like Hibiscus verdcourtii have entirely lost these markings. Others, such as H. richardsonii, show only faint, diminished patterns. That contradiction sparked the team’s investigation.

Genetics behind the bullseye pattern

The researchers focused on the genetic basis for these changes and uncovered a single gene, BERRY1, that largely controls the presence or absence of bullseye markings.

When the gene is active, the plant produces enzymes that turn on pigment synthesis in the petal base. When disrupted or deleted, the flower loses its bullseye.

In H. trionum, BERRY1 works normally, helping form large purple bullseyes. In H. richardsonii, though, the gene is still present but riddled with mutations, including premature stop codons and insertion sequences.

These defects deactivate the gene, meaning it can no longer activate downstream pigment genes like DFR1. In some populations of H. verdcourtii, BERRY1 is entirely missing, and the flowers show no sign of the pattern.

“Floral traits like bullseyes do more than look pretty – they have real impacts on plant reproduction and survival,” said Dr. Edwige Moyroud. “By tracing the genetics behind these petal patterns, we’re beginning to understand how relatively simple mutations can lead to major evolutionary changes.”

Flowers lost bullseyes through mutations

What’s striking is not just that bullseyes disappear, but how often and how similarly this has occurred. Across various Hibiscus species, evolution has repeatedly altered the same gene to yield the same outcome: loss of the bullseye.

This process, called replicated or convergent evolution, is rare at the genetic level and offers powerful insight into how biodiversity arises.

Despite different evolutionary paths, the flowers arrive at similar solutions. These independent losses of BERRY1 or its function suggest strong selective pressure for pattern reduction in some contexts. It also hints at a deeper ecological trade-off.

The cost of keeping the bullseye must outweigh the benefit under certain conditions, or such a change would never persist.

In effect, what seems like a visual downgrade is in fact an adaptation – one that responds to forces beyond pollination alone.

Losing color may help protect flowers

Why would natural selection favor this loss? The answer may lie in the biochemistry of plant pigments.

The same molecular pathway that makes anthocyanins (for color) also makes flavonols, which shield against UV light. These two pigment classes compete for shared building blocks.

In flowers like H. richardsonii with mutated BERRY1, the block on anthocyanin production means more resources shift to flavonols. These flavonols are invisible to bees but may offer better UV protection. Field measurements from the study showed significantly higher flavonol levels in the petal bases of bullseye-less flowers.

In high-UV environments or situations with reduced pollinator reliance, selection may favor flowers that trade color for protection. The balance between attracting insects and shielding reproductive tissues becomes critical.

Flower traits reflect survival

This floral transformation isn’t just about pigment. It reflects how environmental pressures sculpt genetic outcomes over time. For plants, the need to reproduce must align with the need to survive.

“Understanding how floral colours and patterns have evolved gives us insight into broader questions about how diversity arises in nature,” noted Yeo. “It also opens up possibilities for improving pollinator-friendly crops and supporting biodiversity in agricultural systems.”

In agriculture, where yield and pollination are crucial, this knowledge may help design better plant varieties. By modulating genes like BERRY1, scientists could encourage desirable flower traits depending on crop and climate.

Witnessing flower evolution firsthand

This genetic drama isn’t hidden behind lab doors. It is now on full display at the 2025 RHS Chelsea Flower Show, where the Moyroud team is showcasing two Hibiscus species – one with a large bullseye, and one without.

The exhibit includes live imaging with a scanning electron microscope and interactive visualizations of their results. Visitors can see firsthand how flower evolution operates on both genetic and visual levels.

The team’s contribution brings the precision of science into the public eye, transforming a garden staple into a model for evolutionary biology.

Bullseye loss shows how flowers evolve

Every petal carries a message written in molecules. In Hibiscus, that message can vanish as quickly as it appears, erased by mutation, UV rays, or changing pollinator preferences.

The loss of a bullseye might look like a step back – but it’s often a sideways step in nature’s dance of survival.

As this research reveals, biodiversity doesn’t just emerge from change – it emerges from repetition. Nature tries the same path over and over, sometimes reaching different results, sometimes the same.

Through it all, each bloom writes a quiet record of the forces shaping life. And sometimes, that record is written in the pattern of a flower’s fading ring.

The study is published in the journal New Phytologist.

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