Journal Article

Usefulness and limitations of thermal performance curves in predicting ectotherm development under climatic variability

Mahdjoub, Hayat, Rohner, Patrick T., Roy, Jeannine, Blanckenhorn, Wolf U., Khelifa, Rassim

2019

Overview

Thermal performance curves (TPCs) have been estimated in multiple ectotherm species to understand their thermal plasticity and adaptation and to predict the effect of global warming. However, TPCs are typically assessed under constant temperature regimes, so their reliability for predicting thermal responses in the wild where temperature fluctuates diurnally and seasonally remains poorly documented. Here, we use distant latitudinal populations of five species of sepsid flies (Diptera: Sepsidae) from the temperate region (Europe, North Africa, North America) to compare estimates derived from constant TPCs with observed development rate under fluctuating temperatures in laboratory and field conditions. TPCs changed across gradients in that flies originating from higher latitudes showed accelerated development at higher temperatures, an adaptive response. TPCs were then used to predict development rates observed under fluctuating temperatures; these predictions were relatively accurate in the laboratory but not the field. Interestingly, the precision of TPC predictions depended not only on the resolution of temperature data, with daily and overall temperature summing performing better than hourly temperature summing, but also on the frequency of temperatures falling below the estimated critical minimum temperature. Hourly temperature resolution most strongly underestimated actual development rates, because flies apparently either did not stop growing when temperatures dropped below this threshold, or they sped up their growth when the temperature rose again, thus most severely reflecting this error. We conclude that when flies do not encounter cold temperatures, TPC predictions based on constant temperatures can accurately reflect performance under fluctuating temperatures if adequately adjusted for nonlinearities, but when encountering cold temperatures, this method is more error‐prone. Our study emphasizes the importance of the resolution of temperature data and cold temperatures in shaping thermal reaction norms. Thermal performance curve (TPC) can be used to predict the response of ectotherms to thermal changes. This study, carried out on coprophagous flies, highlights the usefulness and limitations of TPC in predicting the effect of temperature fluctuations on development rate under laboratory and field conditions.

• Publisher: Wiley,Blackwell Publishing Ltd
• Subject: Africa, Northern / Altitude / animal ecology / Animals / chilling / Climate Change / Climate variability / Cold / ectothermy / Europe / Flies / Global warming / Herbivores / High temperature / Laboratories / latitude / Norms / North America / Northern Africa / Performance prediction / plasticity / Reliability analysis / Reproducibility of Results / RESEARCH ARTICLE / Sepsidae / temperate zones / Temperature / temperature variation / thermal adaptation / Variation