Abstract
Extreme weather events are becoming more frequent, severe, and/or widespread as a consequence of anthropogenic climate change. While the economic and ecological implications of these changes have received considerable attention, the role of evolutionary processes in determining organismal responses to these critical challenges is currently unknown. Here we develop a novel theoretical framework that explores how alternative pathways for adaptation to rare selection events can influence population‐level vulnerabilities to future changes in the frequency, scope, and intensity of environmental extremes. We begin by showing that different life histories and trait expression profiles can shift the balance between additive and multiplicative properties of fitness accumulation, favoring different evolutionary responses to identical environmental phenomena. We then demonstrate that these different adaptive outcomes lead to predictable differences in population‐level vulnerabilities to rapid increases in the frequency, intensity, or scope of extreme weather events. Specifically, we show that when the primary mode of fitness accumulation is additive, evolution favors ignoring environmental extremes and lineages become highly vulnerable to extinction if the frequency or scope of extreme weather events suddenly increases. Conversely, when fitness accumulates primarily multiplicatively, evolution favors bet‐hedging phenotypes that cope well with historical extremes and are instead vulnerable to sudden increases in extreme event intensity. Our findings address a critical gap in our understanding of the potential consequences of rare selection events and provide a relatively simple rubric for assessing the vulnerabilities of any population of interest to changes in a wide variety of extreme environmental phenomena.
Highlights
Long‐term success in biology is sensitive to variation in performance (Frank & Slatkin, 1990; Lewontin & Cohen, 1969)
Our results challenge the previously suggested idea that species that have been exposed to more variable environments are better suited to cope with climate change and demonstrate instead that vulnerability is likely to depend on the interaction between life‐history and spatiotemporal variation (Lawson et al, 2015; McLean, Lawson, Leech, & Pol, 2016; Scheiner, 2014)
We have shown that if a sufficient fraction of individuals in a population is able to escape the negative consequences of extreme events, populations will typically evolve phenotypes that maximize fitness under moderate conditions and will subsequently become most vulnerable to changes in the frequency or scope of environmental extremes
Summary
Long‐term success in biology is sensitive to variation in performance (Frank & Slatkin, 1990; Lewontin & Cohen, 1969). In evolutionary scenarios that emphasized the multiplicative aspects of fitness accumulation (green background, Figures B.2, B.4, B.5 and B.7 in Appendix B), all simulated populations exhibited conservative phenotypes by generation 2,000 and were subsequently unaffected by changes in the scope or frequency of similar environmental extremes (Figure 3b,c, Figures B.2b,c, B.5c and B.7b,c in Appendix B) These same populations were highly sensitive to changes in the height of floods because their nesting phenotype was not conservative enough to protect them against higher than expected water levels (Figure 3a, Figures B.2a, B.5a and B.7a in Appendix B), and because historically opposite forces of selection (i.e., flooding vs predation) had largely depleted intrapopulation variation in nest height. The number of populations that evolved bet‐hedging (high‐nesting) phenotypes increased (Figures B.1, B.3b, B.8b and B.9b in Appendix B), and populations that evolved under a wider range of conditions became vulnerable to changes in the intensity, but not the scope or frequency of environmental extremes (Figures B.2 and B.5 in Appendix B)
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