Here we combined controlled experiments and field surveys to determine if estimates of heat tolerance predict distributional ranges and phenology of different Drosophila species in southern South America. 

We contrasted thermal death time curves, which consider both magnitude and duration of the challenge to estimate heat tolerance, against the thermal range where populations are viable based on field surveys in an 8-yr longitudinal study. 

We observed a strong correspondence of the physiological limits, the thermal niche for population growth, and the geographic ranges across studied species, which suggests that the thermal biology of different species provides a common currency to understand how species will respond to warming temperatures both at a local level and throughout their distribution range. 

Our approach represents a novel analytical toolbox to anticipate how natural communities of ectothermic organisms will respond to global warming.

Fieldwork and heat tolerance assays

In this study, adult flies of D. simulans, D. hydei, D. subobscura and D. immigrans were collected during the Austral spring and summer of 2018 and 2019 from eleven localities in Chile. Then, 15 laboratory population lines were established in the laboratory. Under controlled conditions, we measured heat knockdown times of individuals belonging to each population. We complemented our dataset with measurements of thermal tolerance previously obtained in our research group.

Estimation of heat tolerance across species and populations

We employed thermal death-time (TDT) curves to quantify and compare heat tolerance across populations and species. For this purpose, linear models between assay temperatures and knockdown or death times were fitted to estimate the coefficients of the TDT curves. Linear models also included the ambient temperature from each locality as a predictor.

Study of the thermal niche for population growth

We combined monthly estimates of population size for 16 drosophilid species in Santiago (Chile) with mean ambient temperature records for the 1984 – 1991 period. With this dataset, we adjusted the population growth rate depending on ambient temperature following a quadratic regression. Afterward, we standardized the knockdown time for 1 h and 12 hours using the TDT coefficients to define a consistent critical temperature window among species. Finally, we predicted how different Drosophila species will be affected by warming conditions combining the equations obtained from quadratic regression with historical records of daily temperatures.

This dataset contains: 

- 11 Excel files with temperature data of each sampling locations (actual period).

- 8 CSV files with temperature data in Santiago (the period between 1984-1991).

-1 Excel file with heat tolerance data ("tolernce.xlsx")

-1 Excel file with phenology data ("phenology_drosophila.xlsx")

-1 R-file with the R-code to repeat the analysis and plots of the article.