Tropical butterflies “hedge their bets” with mating tactics to adapt to extreme seasons

Nymphalid butterflies in the Peruvian Amazon are adapting their mating behaviour to climate change

New research from Queen Mary University of London shows how extreme seasonal patterns are causing rainforest butterflies to adapt their reproductive strategies at a rapid pace, with implications for species resilience under accelerating climate disruption. 

The researchers, led by PhD student Marcus Hicks under supervision by Dr Vicencio Oostra at Queen Mary, studied the reproductive patterns of brush-footed butterflies (the family Nymphalidae) in a seasonal rainforest in the Peruvian Amazon. They collaborated closely with co-authors at the Alliance for a Sustainable Amazon’s Finca Las Piedras field station in southeastern Peru, at the Pontifical Catholic University of Peru, Lund University, and the University of Nottingham. Their findings have been published in Ecology Letters. 

Large parts of the Amazon experience strongly seasonal rainfall and a pronounced, annual dry season, but the way in which insects respond to these seasonal changes has so far been studied very little.  

Hicks and his colleagues documented for the first time how the reproductive behaviour of nymphalids changes with the seasons in the Amazon. This is described as ‘seasonal reproductive plasticity’, where non-genetic variations, like changes in the local climate, result in a change in a species' traits, such as development or behaviour.  

‘Surprising variation’ in reproductive strategies 

They focused on two butterfly species in the genus Catonephele and found that, whilst both species reduced egg production during the dry season, only one of the species underwent a ‘reproductive diapause’, meaning that adult females stopped developing eggs and reduced their mating activity. The other species continued to mate and reproduce, albeit at a reduced rate. 

The reproductive patterns in both species seemed to be driven by the maximum daily temperature, showing how the same cue can produce different developmental and behavioural outcomes in closely related species. 

Hicks said: “We were surprised to see so much variation in reproductive strategies across this group of butterflies, even within the same populations. In temperate butterflies you’d expect to see diapause in almost 100% of individuals in the winter. 

“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.” 

A ‘vital step forward’ in understanding how insects respond to seasonal changes in the tropics 

The study’s findings reinforce how seasonality is a key driver of flexible adaptations in the timing of reproduction. This carries implications for the evolution of many traits in the South American tropics.  

Hicks continued, “To me, this study represents a vital step forward in our understanding of how Amazonian insects respond to seasonal environments. 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.  

“Given the great ecological and economic significance of insects, understanding how they will respond to these changes is of utmost importance for ensuring future ecosystem health and resilience.” 

University of Nottingham PhD student Jamal Kabir, who contributed to butterfly field collections and early sample processing in the Peruvian Amazon, said “Understanding how tropical insects respond to changing seasonal conditions is becoming increasingly valuable as climate change alters rainfall and temperature patterns across the Amazon.”