Predicting virus evolution: the relationship between genetic robustness and evolvability of thermotolerance

Evolutionary biologists often seek to infer historical patterns of relatedness among organisms using phylogenetic methods and to gauge the evolutionary processes that determine variation among individuals in extant populations. But relatively less effort is devoted to making evolutionary biology a truly predictive science, where future evolutionary events are precisely foreseen. Accurate predictions of evolvability would be particularly useful in the evolution of infectious diseases, such as the ability to preemptively address the challenge of pathogens newly emerging in humans and other host populations. Experimental evolution of microbes allows the possibility to rigorously test hypotheses regarding pathogen evolvability. Here, we review how genetic robustness was a useful predictor in gauging which variants of RNA virus varphi6 should evolve faster in a novel high-temperature environment. We also present new data on the relative survival of robust and brittle viruses across elevated temperatures and durations of ultraviolet exposure, to infer a possible mechanism for robustness. Our work suggests that virus adaptability in a new environment can be predicted given knowledge of virus canalization in the face of mutational input. These results hint that accurate predictions of virus evolvability are a realistic possibility, at least under circumstances of adaptive thermotolerance.