This blog post is provided by Ignacio Peralta-Maraver and tells the #StoryBehindThePaper for the article “Warm acclimation reduces the sensitivity of Drosophila species to heat stress at ecologically relevant scales”, which was recently published in the Journal of Animal Ecology. In their study, Ignacio and colleagues tested the acclimation capacity of four Drosophila species, revealing that it is closely associated with temperatures experienced during their development.

There is increasing urgency for more precise predictions to efficiently diagnose and anticipate the response of the organisms in the rapidly warming world. Rising temperatures are pushing many species to their physiological limits, increasing their risk of extinction unless they can adapt. This challenge is especially acute for ectotherms, which mostly rely on environmental temperature to regulate their own body temperature. To understand how these organisms will cope with rising temperatures, researchers have spent decades measuring their heat limits in laboratory experiments. These studies have shed some light on how Global Warming affects survival, distribution, and overall fitness of ectotherms.

How well do lab-based heat limits predict what happens in nature?

That question is more complex than it seems. Traditionally, heat tolerance in ectotherms has been assessed by measuring the highest temperature they can withstand before losing function, often treated as a fixed critical limit. While this approach is still widely used to estimate heat vulnerability, it comes with significant limitations. First, estimates of critical limits varies depending on the methodology, making comparisons across studies difficult. More critically, it focuses solely on heat intensity while overlooking exposure duration—even though thermal stress is cumulative over time. Furthermore, relying on a static threshold is unrealistic, as thermal regimes in nature are dynamic.

Most importantly, traditional thermal measurements often fail to account for thermal acclimation—the ability of organisms to adjust to changing temperatures. An interesting aspect of acclimation is how exposure to variable temperatures during early development can shape thermal limits later in the life cycle. This phenomenon, known as developmental acclimation, suggests that early-life exposure to high thermal conditions could enhance resilience to heat stress in adult stages. Yet, previous research has often concluded that ectotherms have a surprisingly low capacity for acclimation, with even the most tolerant species showing only minimal reductions in overheating risk after acclimation.

What if we have been underestimating the ability to acclimate of ectotherms?

Latest research in global warming ecology suggests that the way we measure heat tolerance in the lab may be obscuring the true acclimation potential of ectotherms. Indeed, thermal acclimation capacity depends on key factors such as the rate at which temperature is increased (ramping rate) and the duration of exposure to new temperatures. Yet, many experiments fail to account for these factors—either by not allowing enough time for acclimation to occur or by using heating rates that far exceed what animals experience in nature.

Do small temperature changes during development impact heat tolerance in ectotherms?

In a recent paper published in Journal of Animal Ecology, we explore this question using a cumulative temperature-time framework, which considers both the magnitude of temperature and the exposure time to predict survival under real-world thermal fluctuations. The analytical framework of this study, also known as thermal tolerance landscapes (Fig. 1), was first introduced in a Perspectives seminar paper published in Functional Ecology in 2014, but it has recently been updated specifically to adapt thermal tolerance assessments under more realistic variable environments. This approach allowed us to bridge the gap between lab experiments and field conditions.

We tested the acclimation capacity of four Drosophila species—two heat-adapted and two cold-adapted species. This time, our findings revealed that Drosophila can physiologically adjust their heat tolerance based on developmental temperature, demonstrating remarkable acclimatory capacity along an acclimation gradient from 18°C to 30°C. The ecological implications of this acclimation are striking. Our models predict that heat-acclimated individuals can persist year-round in the field, while in cold adapted species those developed under cooler conditions struggle to survive as temperatures rise.

Interestingly, we also found that acclimation capacity follows a non-linear pattern, showing a plateau at high acclimation temperatures. This finding raises concerns about how organisms will cope with increasingly frequent and intense heat waves. If acclimation history does not align with shifting thermal conditions, mortality rates could increase, particularly for species with limited plasticity. Expanding this framework to account for acclimation dynamics over time will be crucial for predicting how different organisms might buffer against heating stress. By integrating acclimation into thermal tolerance models, we can move beyond static assessments of heat limits and develop more realistic predictions of species’ resilience to climate change.

Read the paper

Read the full paper here: https://doi.org/10.1111/1365-2656.70018

About the Author

I am a postdoctoral researcher with a strong passion for predicting how organisms respond to climate change. My work integrates ecophysiology, theoretical ecology, experimental research, and predictive modeling to develop tools that enhance our understanding of species resilience in a warming world.