Climate change impacts on population growth across a species’ range differ due to nonlinear responses of populations to climate and variation in rates of climate change

RESEARCH ARTICLE Climate change impacts on population growth across a species’ range differ due to nonlinear responses of populations to climate and variation in rates of climate change Allison M. LouthanID1,2*, William Morris1 1 Biology, Duke University, Durham, North Carolina, United States of America, 2 Division of Biology, Kansas State University, Manhattan, Kansas, United States of America * amlouthan@ksu.edu Abstract Impacts of climate change can differ substantially across species’ geographic ranges, and impacts on a given population can be difficult to predict accurately. A commonly used approximation for the impacts of climate change on the population growth rate is the prod- uct of local changes in each climate variable (which may differ among populations) and the sensitivity (the derivative of the population growth rate with respect to that climate vari- able), summed across climate variables. However, this approximation may not be accu- rate for predicting changes in population growth rate across geographic ranges, because the sensitivities to climate variables or the rate of climate change may differ among popula- tions. In addition, while this approximation assumes a linear response of population growth rate to climate, population growth rate is typically a nonlinear function of climate variables. Here, we use climate-driven integral projection models combined with projections of future climate to predict changes in population growth rate from 2008 to 2099 for an uncommon alpine plant species, Douglasia alaskana, in a rapidly warming location, southcentral

Alaska USA. We dissect the causes of among-population variation in climate change impacts, including magnitude of climate change in each population and nonlinearities in population response to climate change. We show that much of the variation in climate change impacts across D. alaskana’s range arises from nonlinearities in population response to climate. Our results highlight the critical role of nonlinear responses to climate change impacts, suggesting that current responses to increases in temperature or changes in precipitation may not continue indefinitely under continued changes in climate. Further, our results suggest the degree of nonlinearity in climate responses and the shape of responses (e.g., convex or concave) can differ substantially across populations, such that populations may differ dramatically in responses to future climate even when their cur- rent responses are quite similar. PLOS ONE PLOS ONE | https://doi.org/10.1371/journal.pone.0247290 March 3, 2021 1 / 20 a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 OPEN ACCESS Citation: Louthan AM, Morris W (2021) Climate change impacts on population growth across a species’ range differ due to nonlinear responses of populations to climate and variation in rates of climate change. PLoS ONE 16(3): e0247290. https://doi.org/10.1371/journal.pone.0247290 Editor: Ines Iba´ñez, University of Michigan, UNITED STATES Received: May 22, 2020 Accepted: February 4, 2021 Published: March 3, 2021 Copyright: © 2021 Louthan, Morris. This is an open access article distributed under the terms of

the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: The minimal data are deposited in figshare: 10.6084/m9.figshare. 13911755. Code available from the authors on request. Funding: Research was supported by Strategic Environmental Research and Development Program Contract W912HQ15C0051, awarded to WFM (https://www.serdp-estcp.org/), and by USDA National Institute of Food and Agriculture, Hatch project 1016746 (AML). The funders played no role in study design, data collection and