A bright red splash on a butterfly’s wing is more than a pretty pattern. It is a warning label, honed by millions of years of natural selection, that tells birds and lizards: eating me will make you sick. Now, a study published in May 2026 in PLOS Biology reveals something striking about how those warning labels get built. Seven butterfly lineages and a day-flying moth, some of which last shared a common ancestor 120 million years ago, all arrived at nearly identical red-and-black color schemes by toggling the same two genes: ivory and optix.
The finding suggests that when the evolutionary pressure is strong enough, biology does not reinvent the wheel. It reaches for the same wrench, again and again.
Two genes, eight lineages, one solution
The research team, led by scientists at the University of York, sequenced genomes across eight distantly related lineages of Lepidoptera, the insect order that includes butterflies and moths. In every lineage, variation in bold warning coloration mapped back to the same two genomic regions: one near ivory and one near optix. Different combinations of variants at these two sites determined whether red patches appeared on the wings, how large they were, and how they contrasted against black backgrounds.
“The repeated use of the same genes across such deep timescales is unlikely to be due to chance alone,” said Kanchon Dasmahapatra, a senior author and evolutionary biologist at the University of York. He described the pattern as evidence that evolution often follows predictable genetic paths rather than stumbling on new solutions each time.
The divergence times involved are vast. Some of the lineages in the study split from one another roughly 120 million years ago, during the Cretaceous period, when dinosaurs still dominated the planet. Yet despite having no recent common ancestor, these species converged on the same molecular toolkit for advertising their toxicity. The study also found that the day-flying moth in the dataset carries a large chromosomal inversion, a structural rearrangement that locks favorable color-pattern gene variants together, mirroring a mechanism already documented in butterflies.
A pattern that keeps showing up
The new results do not exist in a vacuum. Over the past decade, genomic research has repeatedly shown that Lepidoptera rely on a surprisingly small set of genes to generate their dazzling variety of wing patterns.
A 2014 study in Nature Communications demonstrated that variation near the gene WntA explains parallel banded and striped wing patterns in butterfly lineages that diverged more than 65 million years ago. Different species arrived at comparable visual designs by altering regulatory DNA near the same developmental gene, not by evolving new proteins from scratch.
Separate work on cis-regulatory elements called enhancers showed that mimicry in wing patterns is often driven by small tweaks to genetic “dimmer switches” that control when and where pattern genes are active. These regulatory changes can produce dramatically different wing designs without altering the underlying protein. Another gene, cortex, has been identified as a controller of both mimicry and camouflage across multiple Lepidoptera groups, capable of toggling between drab brown forms and vivid warning displays depending on which variant an individual carries.
Together with the new ivory and optix findings, this body of work paints a consistent picture: the genomic toolkit for insect wing coloration is compact, and natural selection draws on the same components repeatedly when the stakes are high.
Not every species follows the same playbook
Before declaring evolution predictable, there is an important caveat. Monarch butterflies, perhaps the most recognizable warning-colored insect in North America, appear to build their iconic orange-and-black wings through a different genetic route entirely. Research has linked monarch wing pigmentation to a myosin gene, a type of motor protein with no obvious connection to the ivory–optix patterning system. Monarchs advertise their toxicity (acquired by sequestering poisons from milkweed) with a color scheme that looks superficially similar to other warning patterns, yet the molecular machinery underneath is distinct.
This means the ivory–optix system represents one major route to warning coloration in Lepidoptera, not the only route. Evolution, it seems, is constrained in some lineages but retains the flexibility to explore alternative paths in others.
Open questions and missing data
Several gaps remain. No published field studies have yet measured how specific ivory or optix variants affect actual survival rates in wild populations. The link between gene variant and color pattern is well established at the molecular level, but the critical next step, showing that a slightly larger or brighter red patch translates into fewer attacks by real predators in natural habitats, has not been quantified for these loci. Controlled experiments with bird predators could test this, but such data are not yet available.
The study’s taxonomic scope also has limits. All eight lineages belong to Lepidoptera, an order already famous for its rich wing-pattern diversity and well-characterized developmental genetics. Whether ivory and optix play any role in warning coloration in beetles, wasps, poison frogs, or other vividly colored organisms is entirely unaddressed. Those groups may rely on completely different sets of genes to produce their danger signals.
Researchers have speculated that ancestral regulatory networks might link warning coloration to other traits such as thermoregulation or mate selection, which could help explain why the same genes keep getting recruited. But those connections remain hypothetical without direct experimental evidence.
What this means for how we understand evolution
For decades, biologists have debated how much of evolution is driven by random genetic drift versus constrained by the architecture of genomes. The ivory–optix findings land squarely on the “constrained” side of that debate, at least for one high-stakes trait in one major insect order. When survival depends on sending a clear, unmistakable signal to predators, evolution does not appear to wander freely through genetic space. It returns to the same addresses in the genome.
That does not mean all of evolution is predictable. The monarch counterexample shows that alternative solutions persist, and the broader question of whether similar genetic constraints operate in vertebrates, plants, or microbes remains wide open. But for the butterflies and moths that share this planet with us, the message is clear: given the same life-or-death problem, separated by 120 million years, evolution kept writing the same answer.
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*This article was researched with the help of AI, with human editors creating the final content.
