Butterflies that look identical to predators are using scent to find mates, a new study reveals. Hundreds of species in Central and South America share similar color patterns as a warning signal, but this visual mimicry creates a mating challenge. New research shows these butterflies, even those that appear indistinguishable, produce unique scents via pheromones to identify their own kind.
Hidden Clues in Butterfly Scents
Even among strikingly similar species, butterflies possess distinct scents. This subtle chemical difference is crucial for reproduction. Scientists discovered that these lookalike butterflies can differentiate each other through pheromones, chemicals released for olfactory communication. This finding is particularly important for understanding species evolution in groups that have undergone rapid radiation.
“Having the reference genomes for the two groups of glasswing butterflies, Mechanitis and Melinaea, allowed us to take a closer look at how they have adapted to life in such close proximity to their relatives,” said study senior author Dr. Caroline Bacquet. “These butterflies share the responsibility of warding off predators by displaying similar color patterns, and by producing different pheromones they can successfully find mates and reproduce.”
Genetics of Mimicry
An international team of scientists, led by the Wellcome Sanger Institute, sequenced the genomes of dozens of glasswing butterfly species. They focused on two groups known for rapid speciation. Glasswing butterflies, with over 400 species found across Central and South America, are often used as indicator species due to their reflection of the broader insect ecosystem’s health.
The research mapped the butterflies’ genetics, leading to the identification of six subspecies previously thought to be distinct enough to be separate species. The team also generated ten high-quality reference genomes, now available for scientific research. This genetic mapping helps explain the butterflies’ survival strategy: visual mimicry for predator deterrence, coupled with olfactory cues for mate recognition.
Rapid Evolution and Chromosomal Clues
A surprising discovery involved the butterflies’ DNA. While most butterflies have 31 chromosomes, glasswing species showed variations ranging from 13 to 28. These chromosomal rearrangements, which involve rearranging genes rather than changing them, significantly impact reproduction. Butterflies with different chromosome counts produce sterile offspring, making it crucial to mate with the correct species.
Scientists theorize that this high degree of chromosomal rearrangement is a key driver behind the rapid evolution of new species within this group. “Once a population’s chromosome count shifts, it effectively becomes its own species, better able to adapt to local environments or food sources,” explained Dr. Eva van der Heijden, the study’s first author. “However, until now, there was no genetic resource that allowed us to robustly identify different species, and it is difficult to monitor and track something that you can’t identify easily.”
Conservation Implications
Understanding how these butterflies rapidly evolve could offer insights into broader evolutionary questions. It may shed light on why some insects diversify extensively while others do not, and how environmental pressures drive adaptation. This knowledge could also have applications in agriculture and pest control.
Dr. Joana Meier, a senior author at the Wellcome Sanger Institute, stressed the importance of this research in the context of the current extinction crisis. “Comparing butterflies that rapidly form new species to others that do not could benchmark how common this is in insects and highlight the factors involved,” she stated. “This, in turn, could identify any species that require closer conservation and possibly identify genes that are important in the adaptation process and might have uses in agriculture, medicine, or bioengineering. This research would not have been possible without global collaboration. We have one planet, and we must work together to understand and protect it.”
The findings were published in the journal Proceedings of the National Academy of Sciences.
