Researchers 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, published in the journal Nature Ecology & Evolution on October 24, 2025, provides insight into how insects adapt to their environments and may inform future conservation efforts in the face of climate change.
Insects, particularly tropical butterflies, exhibit remarkable adaptability, with some species capable of changing their coloration and other traits with the seasons. This phenomenon, known as plasticity, is crucial for survival but has long puzzled scientists regarding its evolutionary origins.
Key Findings on Butterfly Adaptation
A team led by Professor Antónia Monteiro from the NUS Department of Biological Sciences focused on the African butterfly, Bicyclus anynana, which displays significant differences in wing patterns between wet and dry seasons. During the wet season, these butterflies develop larger eyespots, while smaller eyespots emerge during the dry season. This adaptation enhances their chances of survival in varying environments.
Previous research indicated that the temperature experienced by caterpillars influences the size of the eyespots, a response that appears unique to the satyrid group of butterflies. These butterflies are characterized by their predominantly brown wings adorned with distinctive eyespots.
The new study pinpointed a master instruction gene known as Antennapedia (Antp), which regulates the development of eyespots in satyrid butterflies. Researchers found that the activity of this gene fluctuates depending on the temperatures at which the butterflies are raised. Disrupting the gene’s activity in two different satyrid species resulted in a reduction of eyespot size, particularly when the butterflies were raised in warmer conditions, confirming the gene’s role in seasonal size changes.
The Role of Genetic Switches in Evolution
In addition to the Antp gene, the research team uncovered a previously unknown DNA switch, referred to as a promoter, which exists exclusively in satyrid butterflies. This switch activates the Antp gene specifically in the eyespot central cells, and disabling it hindered the butterflies’ ability to adapt their eyespot size to changing temperatures. This finding suggests that such genetic elements play a significant role in the evolution of seasonal adaptability.
Dr. Tian Shen, the lead author of the study and former graduate student and postdoctoral fellow at NUS, remarked on the significance of their 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 advances understanding of butterfly biology but also emphasizes the potential for genetic studies to contribute to conservation strategies in an era of rapid environmental change.