A new study suggests otherwise, at least when it comes to the wings of butterflies and moths.
Scientists have discovered that distantly related species of Lepidoptera, the insect order encompassing butterflies and moths, have been using the exact same genetic mechanisms to produce identical wing color patterns for over 120 million years.
Researchers identified two genes, named ivory and optix, whose expressions are governed by regulatory “switches” that produce identical color patterns across species.
In other words, it is not the genetic code that changes from species to species, but the way that code is turned on or off.
Ivory and optix control convergent phenotypes across multiple species – © PLOS BiologyTo confirm their findings, the team went beyond association analysis.
Evolution was supposed to be unpredictable. A new study suggests otherwise, at least when it comes to the wings of butterflies and moths.
Scientists have discovered that distantly related species of Lepidoptera, the insect order encompassing butterflies and moths, have been using the exact same genetic mechanisms to produce identical wing color patterns for over 120 million years. The findings, published in the journal PLOS Biology, raise serious questions about just how “random” evolutionary adaptation really is.
The ability of some butterfly and moth species to display strikingly similar warning patterns has long fascinated entomologists. These patterns serve a specific survival function: they signal to predators that the insect is toxic or unpalatable, a strategy that works better the more species share it. What was less understood, until now, is why so many genetically distant species keep arriving at the same visual solutions, and how, at the molecular level, they pull it off.
A Genetic Trick Repeated Since the Age of the Dinosaurs
The research focused on a phenomenon called Müllerian mimicry, in which toxic species independently evolve the same warning patterns, and Batesian mimicry, in which non-toxic species adopt the appearance of toxic ones to avoid predation. The Monarch butterfly and the Viceroy offer a well-known illustration of this complexity: long considered a Batesian mimic of the Monarch, the Viceroy was later found to be distasteful to predators as well, placing it firmly in the Müllerian mimic category.
Phylogenetic relationships and mimetic phenotypes – © PLOS Biology
According to the study, an international team of scientists examined Lepidoptera species whose evolutionary lineages diverged up to 120 million years ago. The team investigated seven butterfly lineages and a day-flying moth, and found that across all of them, the same genetic architecture was at work. “Butterflies and moths have been using the exact same genetic tricks repeatedly to achieve similar color patterns since the age of the dinosaurs,” said Kanchon Dasmahapatra of the University of York, a co-author of the study.
Two Genes, Many Switches
The central discovery concerns not the genes themselves, but the regulatory mechanisms controlling them. Researchers identified two genes, named ivory and optix, whose expressions are governed by regulatory “switches” that produce identical color patterns across species. In other words, it is not the genetic code that changes from species to species, but the way that code is turned on or off.
In moths, the mechanism operates slightly differently. According to the authors, Chetone moths, a genus of tiger moth from neotropical regions known to mimic both toxic Ithomiini butterflies and Heliconius butterflies, use what the researchers describe as an “inversion mechanism,” which essentially flips a chunk of DNA code so that it closely resembles a beneficial butterfly adaptation. The study also included species from the Ithomiini group, described as one of the most well-studied groups of Lepidopterans.
Ivory and optix control convergent phenotypes across multiple species – © PLOS Biology
To confirm their findings, the team went beyond association analysis. “Not only did we find an association between a gene and colour variation in various species, but we also showed that breaking that gene through genetic modification actually changes the butterfly’s color,” said Eva van der Heijden of the University of Cambridge, a co-author of the study. “This confirms our association analysis identified the correct gene.”
What This Means for Understanding Adaptation
The implications of the research extend beyond the study of wing patterns. By identifying what the researchers call “mutation hotspots“, specific points in the genome that allow for rapid adaptation, the study suggests that evolutionary change may follow more predictable pathways than previously assumed.
Detailed phenotypic and functional analysis in Mechanitis messenoides – © PLOS Biology
According to Popular Mechanics, which reported on the findings, this predictability could offer researchers new insights into how species might respond to future environmental pressures, including climate change. The study’s framing challenges the traditional view, rooted in Darwinian theory, that mutations driving natural selection are essentially random. While Charles Darwin laid out the foundational mechanics of how life differentiates through natural selection and random mutation, instances of convergent and parallel evolution have long complicated that picture.
The research centers notably on Heliconius butterflies, a group recognized for its extensive use of both Müllerian and Batesian mimicry, and represents a collaboration between institutions across multiple countries. As Dasmahapatra put it, “evolution can be surprisingly predictable“, a conclusion that, coming from a study spanning 120 million years of insect history, carries considerable weight.
