Scientists at the National University of Singapore (NUS) have identified a simple DNA switch that enables tropical butterflies to alter the size of their wing eyespots in response to seasonal temperature variations. This discovery sheds light on how environmental sensitivity evolves in these insects and could have implications for understanding adaptation to climate change. The findings were published in the journal Nature Ecology & Evolution on October 24, 2025.
Tropical butterflies exhibit remarkable seasonal flexibility, known as plasticity, which allows them to survive in diverse environments. This ability often manifests through changes in colour and wing patterns, but the evolutionary origins of such adaptations have long puzzled researchers. The team, led by Professor Antónia Monteiro from the NUS Department of Biological Sciences, focused on the African butterfly, Bicyclus anynana, a species known for its striking differences between wet and dry seasons.
During the wet season, these butterflies develop larger eyespots, which reduce in size during the dry season. These variations enhance survival chances in each respective environment. Previous research indicated that the temperature at which caterpillars are raised significantly influences this size change, highlighting a unique response among the satyrid group of butterflies, characterized by their brown wings and distinctive eyespots.
In the latest study, the team pinpointed a master instruction gene called Antennapedia (Antp), which governs the development of eyespots in satyrid butterflies. They discovered that the activity of this gene varies with the temperature conditions experienced during the butterflies’ rearing. Disruption of the Antp gene in two different satyrid species led to a noticeable reduction in eyespot size, particularly when raised in warmer temperatures, confirming the gene’s role in seasonal size adjustments.
The research also unveiled a previously unknown DNA switch, referred to as a “promoter,” which is unique to satyrid butterflies. This switch activates the Antp gene specifically in the central cells of the eyespots. When the switch was disabled, the butterflies’ ability to adapt their eyespot size with temperature diminished, indicating that this genetic element plays a crucial role in the evolution of their seasonal adaptability.
Dr. Tian Shen, the lead author of the study, remarked on the significance of the findings, stating, “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.”
This research not only enhances our understanding of butterfly adaptation but also highlights the intricate connections between genetics and environmental changes. As climate change continues to affect ecosystems worldwide, insights from studies like this could be vital for conservation efforts aimed at protecting vulnerable species.
