Fig 4. Differences between average temperatures in early spring (March) and the maximum temperatures the following month (April).

The temperatures experienced during the adult stage of D. melanogaster in nature may differ from the temperatures experienced during development. To quantify these temporal changes in temperature, we calculated the differences between average temperatures in March and the maximum temperatures in April in the Northern hemisphere (delta temperature (°C)). Temperature data was obtained from WorldClim and are interpolations of data from 1950–2000 [53]. The map was produced with the raster package in R vers. 2.2–5 [54].