ABSTRACT
The biochemical properties underpinning the genotype-phenotype map can exert major influence over evolutionary rates and trajectories. Yet, the constraints set by these molecular features are often neglected within eco-evolutionary frameworks. Here, by applying a biophysical model of protein evolution, we demonstrate that rising global temperatures are expected to intensify natural selection genome-wide by increasing the effects of sequence variation on protein phenotypes. Our model further suggests that thermal adaptation will not alleviate this effect; warm and cold adapted species are expected to show the same temperature-dependent increase in the strength of selection. We tested these predictions using lines of seed beetle evolved at ancestral or warm temperature for 70-85 generations. According to predictions, fitness effects of induced mutations were stronger at high temperature for both ancestral and warm-adapted lines. We then calculated 98 estimates from the literature, comparing selection on newly induced mutations in stressful and benign environments across a diverse set of ectothermic organisms, ranging from viruses and unicellular bacteria and fungi, to multicellular plants and animals. We first show that environmental stress per se does not increase the strength of selection on new mutations. However, as predicted from the biophysical model, increased temperature does. These results bear witness to and extend the universal temperature dependence of biological rates and have important implications for global patterns of genetic diversity and the rate and repeatability of evolution under environmental change.
SIGNIFICANCE STATEMENT Natural environments are constantly changing so organisms must also change in order to persist. Whether they can do so ultimately depends upon the reservoir of raw genetic material available for evolution, and the efficacy by which natural selection can discriminate among this variation to secure the survival of the fittest. Here we integrate theory from the fields of ecology, genetics and biophysics and combine mathematical modelling and data from organisms across the tree of life, to show that rising global temperatures will universally increase natural selection on DNA sequence variation in cold-blooded organisms. This finding has broad implications for our understanding of biodiversity patterns and suggests that evolution will proceed at an ever accelerating pace under climate warming.