AsianScientist (Dec. 23, 2025) – Scientists in Singapore have discovered a simple genetic mechanism that helps tropical butterflies to change their wing patterns with the seasons. The discovery of this tiny DNA “switch” that responds to temperature, offers fresh insights into how insects evolve the ability to sense and adapt to environmental changes.
Insects often adapt in surprising ways to their surroundings. Some butterflies, for example, change their colours with the seasons. This seasonal flexibility, called plasticity, is vital for survival in unpredictable environments. Yet, the genetic basis for such flexibility has remained largely unknown.
A research team led by Professor Antónia Monteiro from the Department of Biological Sciences at the National University of Singapore (NUS), has now identified a stretch of DNA that helps certain butterflies switch their wing patterns between wet and dry seasons.
Seasonal shape-shifting
“Many tropical butterflies look strikingly different depending on whether they emerge in the dry or wet season. The African butterfly, Bicyclus anynana, the species we study, is one such example,” said Monteiro.
In the wet season, these butterflies develop larger eyespots on their wings. During the dry season, these eyespots are smaller. These seasonal changes help in their survival.
Earlier studies showed that the temperature at which caterpillars develop determines the size of these eyespots. This strong temperature response is unique to satyrid butterflies, a family characterised by their brown wings marked with distinctive eyespots.
The gene behind the change
To understand the genetic machinery behind this transformation, the researchers focused on a master developmental gene called Antennapedia (Antp). This gene controls how eyespots form in satyrid butterflies.
They found that this gene becomes more or less active depending on the temperatures at which the butterflies were raised. When they disrupted the gene in two different satyrid species, the eyespots shrank, especially in butterflies raised at warmer temperatures. This confirmed Antp’s central role in the seasonal size change.
The breakthrough came when the team discovered a previously unknown DNA switch – a promoter – that exists only in satyrid butterflies. This promoter activates the Antp gene specifically in the central cells of eyespots, the cells that determine how large the spots will become.
On disabling this promoter, the butterflies lost much of their ability to adjust eyespot size in response to temperature. This suggests that the evolution of this DNA switch played a key role in giving satyrid butterflies their remarkable seasonal flexibility.
Researchers say that the findings, published in Nature Ecology & Evolution, help understand how animals evolve resilience to environmental changes.
“It is striking that a simple genetic switch can underlie complex environmental sensitivity across a broad group of insects. These findings open the door to future research into the roles such switches play in shaping adaptations, and to insights that could inform conservation in a changing climate,” said Dr Tian Shen, the first author of the paper who conducted the research when he was a graduate student and postdoctoral fellow at NUS.
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Source: National University of Singapore ; Image: Diego Murta/shutterstock
The study can be found at: A novel Hox gene promoter fuels the evolution of adaptive phenotypic plasticity in wing eyespots of satyrid butterflies
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