Predicting temperature mortality and selection in natural Drosophila populations

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Science  04 Sep 2020:
Vol. 369, Issue 6508, pp. 1242-1245
DOI: 10.1126/science.aba9287

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Accounting for heat burdens

As climate warming becomes more and more apparent and influential, there is an increasing desire to predict its long-term impacts on species. Classically, this has been done by extrapolating lethal limits based on those observed in the laboratory. In the real world, however, organisms do not experience a single high temperature that then returns to a comfortable temperature, but rather a series of high temperatures during the hot season. Rezende et al. accounted for these accumulative effects in a dynamic model that accurately predicted empirical patterns in wild fruit fly populations, showing that cumulative effects of warming temperatures can be included in future estimates (see the Perspective by Huey and Kearney).

Science, this issue p. 1242; see also p. 1163


Average and extreme temperatures will increase in the near future, but how such shifts will affect mortality in natural populations is still unclear. We used a dynamic model to predict mortality under variable temperatures on the basis of heat tolerance laboratory measurements. Theoretical lethal temperatures for 11 Drosophila species under different warming conditions were virtually indistinguishable from empirical results. For Drosophila in the field, daily mortality predicted from ambient temperature records accumulate over weeks or months, consistent with observed seasonal fluctuations and population collapse in nature. Our model quantifies temperature-induced mortality in nature, which is crucial to study the effects of global warming on natural populations, and analyses highlight that critical temperatures are unreliable predictors of mortality.

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