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

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 product 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 variable), summed across climate variables. However, this approximation may not be accurate 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 populations. 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 current responses are quite similar.

Life history adaptations to fluctuating environments: Combined effects of demographic buffering and lability

“…In contrast to adaptive demographic buffering, which optimises fitness by reducing the variance of most influential demographic parameters, lability can be adaptive if the benefit of an increase in the arithmetic mean of the annual growth rates through increased demographic parameter means can overcome the negative effect of increased demographic variance on fitness (Box 1 ). Nonlinearity in population and demographic parameter responses to environmental drivers may be common in the wild (Barraquand & Yoccoz, 2013 ; Clark & Luis, 2020 ; Dahlgren et al, 2011 ; Drake, 2005 ; Hansen et al, 2021 ; Jenouvrier et al, 2012 ; Lawson et al, 2015 ; Louthan & Morris, 2021 ; Mysterud et al, 2001 ), highlighting the potential importance of lability as an adaptation to environmental variability. However, with structured life histories the combined effects of nonlinearity in different demographic parameters on fitness are challenging to predict (Koons et al, 2009 ).…”

Responses to desiccation vary among populations of an endemic freshwater isopod,Paramphisopus palustris

“…Some of these differences may be due to intrinsic population sensitivity, intraspecific variation in life history and generation time (e.g. alpine plants, Louthan & Morris, 2021), or local adaptation (e.g. Yilmaz et al., 2020).…”

The Mediterranean bioconstructor Lithophyllum stictiforme shows adaptability to future warming

“…The climate impacts are expressed at various levels of biological organization and often are due to changes in local or regional environmental conditions affecting biological processes such as reproduction and survival (Ådal et al, 2006). Species may respond differently to climate change because of a variety of factors, such as evolutionary history, species interactions, physiology, genetic structure, behavior, and habitat-mediated environmental effects on individuals (Etterson and Shaw, 2001;McCoy and Ragazzola, 2014;Hurd, 2015;Louthan and Morris, 2021). Local habitat conditions can mediate the effects of climate, so populations living in different habitats may exhibit different responses to global changes (Crozier et al, 2008).…”