Flies like it cool: study reveals evolutionary shifts in temperature preference among Drosophila larvae

New research from Queen Mary University of London reveals how fruit fly larvae have repeatedly evolved their temperature preferences, shedding light on the intricate ways animals adapt to their environments. The study, published in iScience, provides crucial insights into how they cope with a changing climate. 

Dr Roman Arguello, Lecturer in Genetics, Genomics and Fundamental Cell Biology at Queen Mary, and colleagues from the University of Lausanne and the University of Cologne, used a combination of behavioural assays, high-resolution larval tracking, and agent-based computational modelling to uncover the evolutionary mechanisms behind temperature preference in eight species of Drosophila larvae. 

Their findings show that rather than evolving new ways of sensing temperature, the larvae have adapted by shifting how their nervous systems weigh warm versus cool avoidance. These subtle yet crucial changes allow closely related species to thrive in a wide variety of thermal environments from cool mountaintops to subtropical zones. 

“It turns out these tiny animals recurrently evolve  small but important strategies to stay comfortable,” said Dr Arguello. “Their ability to fine-tune their behaviour based on local climates gives us insight into how evolution shapes sensory systems and how species might respond to global temperature shifts.” 

By analysing over 2,400 larval movement trajectories across a custom-built thermal arena, the team discovered that species such as D. lutescens and D. santomea, which inhabit cooler environments, showed a marked preference for lower temperatures compared to their sister species living in warmer habitats. These preferences were confirmed across multiple strains per species, highlighting heritable behavioural adaptations. 

Importantly, the work also suggests that well-studied lab strains of D. melanogaster often used as behavioural model organisms may not be representative of the species as a whole, due to striking variability in thermotaxis. 

Poikilotherms like Drosophila – animals whose body temperature depends on external sources – are particularly vulnerable to climate change. Understanding how their thermosensory behaviours evolve provides critical insight into how biodiversity might respond to warming environments. 

“Our work shows that these behaviours are both evolutionarily flexible and quantifiable,” said Dr Arguello. “By studying them in a comparative and experimentally tractable system like Drosophila, we can start to uncover the neural and genetic underpinnings of climate adaptation and how their behaviour might shift under continued environmental change.”