Abstract
As thermal regimes change worldwide, projections of future population and species persistence often require estimates of how population growth rates depend on temperature. These projections rarely account for how temporal variation in temperature can systematically modify growth rates relative to projections based on constant temperatures. Here, we tested the hypothesis that population growth rates in fluctuating thermal environments differ from growth rates in constant conditions, and that the differing thermal performance curves (TPCs) can be predicted quantitatively. With experimental populations of the green alga Tetraselmis tetrahele, we show that nonlinear averaging techniques accurately predicted increased as well as decreased population growth rates in fluctuating thermal regimes relative to constant thermal regimes. We extrapolate from these results to project critical temperatures for population growth and persistence of 89 phytoplankton species in naturally variable thermal environments. These results advance our ability to predict population dynamics in the context of global change.
Author contributions: JRB conceived the study and designed the experiments, with help from JMS, PLT and MIO. JRB carried out the experiments, analyzed the data and wrote the first draft of the manuscript. All authors contributed to writing the manuscript. All authors gave final approval for publication.
Footnotes
Data accessibility: All data will be made available on Dryad should the manuscript be accepted. All code and data for analyses are available at https://github.com/JoeyBernhardt/thermal-variability.
Competing interests: We have no competing interests.