In the seasonal rainforests of the Peruvian Amazon, brush-footed butterflies are making reproductive choices that would baffle their temperate cousins—and the reason reveals how quickly life adapts when the climate itself becomes unpredictable. New research from Queen Mary University of London, led by Ph.D. student Marcus Hicks and Dr. Vicencio Oostra, shows that two closely related butterfly species in the genus Catonephele are responding to extreme seasonal patterns in strikingly different ways, offering a glimpse into how tropical insects might survive accelerating climate disruption.
The research, published in Ecology Letters, documents for the first time how nymphalid butterflies shift their reproductive behavior with the seasons in the Amazon. While both species reduced egg production during the dry season, only one underwent reproductive diapause—a state in which adult females stopped developing eggs and reduced mating activity altogether. The other species kept reproducing, though at a lower rate. What drives these divergent strategies? The same environmental cue: maximum daily temperature. Here lies the surprise: the same signal produced two completely different behavioral outcomes in species that share habitat and ancestry.
This variation stands in sharp contrast to temperate butterflies, where nearly all individuals enter diapause during winter. "We were surprised to see so much variation in reproductive strategies across this group of butterflies, even within the same populations," Hicks explained. The team's hypothesis offers a compelling explanation: these butterflies may be hedging their bets. "One explanation could be that these butterflies are hedging their bets to help them navigate increasingly variable conditions in the tropics. It may be helpful for them to 'play both sides,' with some butterflies continuing to reproduce, and others taking a break during the dry season." By splitting the population's reproductive strategy, neither all-in commitment nor complete shutdown, the species as a whole increases its chances of weathering unpredictable conditions.
The findings matter far beyond the Amazon's remarkable biodiversity. Insects are foundational to tropical ecosystems and economies—they pollinate crops, cycle nutrients, and support food webs. Understanding how they respond to shifting seasonal patterns is crucial as climate change distorts rainfall and temperature regimes across the region. Hicks emphasizes the urgency: "As the rapid impacts of anthropogenic climate change become more pronounced, we are likely to see severe changes to these seasonal patterns in the Amazon."
The research team, which included collaborators at the Alliance for a Sustainable Amazon's Finca Las Piedras field station in southeastern Peru, the Pontifical Catholic University of Peru, Lund University, and the University of Nottingham, conducted painstaking observations of natural populations. Their work demonstrates that seasonality itself is a key driver of flexible adaptations—and that tropical insects may already possess the physiological toolkit to adapt to change, if conditions shift more slowly than current trajectories suggest.
What remains unclear is whether these rapid adaptive shifts will prove sufficient as climate change accelerates beyond the pace of natural evolution. The next chapter of this story will be written by the butterflies themselves, in the decisions they make season after season in a warming Amazon.