Predicting Virus Evolution: The Relationship between Genetic Robustness and Evolvability of Thermotolerance

Abstract

As a naturalist, Charles Darwin was understandably fascinated by the species diversity visible in the natural world. However, he understood little of the invisible realm of genes-the units of inheritance that are passed across generations and contribute to the phenotypic variation evident in biological populations. Yet Darwin showed remarkable insight when formulating his ideas on evolution via natural selection, as a process whereby the environment determines which variants in a population are favored to contribute their traits to succeeding generations, leading to microevolutionary changes over short timescales. Furthermore, Darwin perceptively understood that natural selection is a process that can also primarily account for nature's vast biodiversity-resulting from macroevolution occurring over long timescales-which Darwin described as "endless forms most wonderful" (Darwin 1859).Many modern-day evolutionary biologists are concerned with elucidating patterns of extant diversity, seeking to understand how descent with modification from common ancestry accounts for Earth's myriad forms that have evolved since life arose billions of years ago. In contrast, other evolutionary biologists are largely concerned with the processes of evolutionary change that underlie these patterns, examining how mechanisms such as selection and drift can lead to altered phenotypes and genotypes across relatively few generations. Both camps of evolutionary biologists have increasingly powerful and sophisticated approaches for studying patterns and processes of evolution, allowing more accurate glimpses into the mysterious "black boxes" of past and ongoing evolutionary events (see, e.g., Lenski et al. 2003;Thornton et al. 2003;Vrba and DeGusta 2004;Weinreich et al. 2006).Arguably, evolutionary biology mostly concerns scrutiny of past and present events, rather than forthcoming events, i.e., evolutionary biologists tend to resist the temptation to study and predict how evolution will play out in the future. Such predictive efforts are necessarily more difficult than retrospective analyses, because foretelling the future is inherently less precise than resolving the past. For this reason, relatively less energy has been placed into developing evolutionary biology into a truly predictive science. Of course, like other scientists, evolutionary biologists often make explicit predictions, referred to as hypothesis testing. But there is a distinct difference between formulating a hypothesis that concerns events that have already occurred and formulating a hypothesis that predicts events yet to occur. EVOLVABILITY STUDIED USING MATHEMATICAL THEORY AND BIOLOGICAL EXPERIMENTSMathematical studies in evolutionary biology are sometimes future-minded. For example, John Maynard Smith (1982) famously popularized evolutionary game theory, a discipline that often seeks to mathematically determine whether a population can evolve an unbeatable strategy when dealing with competition for finite resources, such as food, mates, or nesting sites. If this evo...

Evolvability and robustness in populations of RNA virus Φ6

“…We found no evidence that the robust populations were pre-adapted to be more thermotolerant as there was no survival difference between robust and brittle populations at 42.5 and 45°C. However, these measurements were taken for the entire population and there may have been individual clones, which were more thermotolerant (Ogbunugafor et al, 2009). Future work could test if our evolvability results are generalizable to other traits.…”

Why and how genetic canalization evolves in gene regulatory networks

“…However, (i) there is little empirical evidence that genetic canalization can actually evolve in real populations (in particular in sexual species) [28], (ii) quantitative characters are far from being completely canalized, as evidenced by the prevalence of monogenic diseases or lethal mutations, and by the high level of genetic variance in most natural populations [29], and (iii) little is known about how canalization translates into observable properties from real genetic systems. In this paper, we aim to challenge theoretically the limits and the prediction power of the “canalizing gene networks” theory.…”

Selection for thermostability can lead to the emergence of mutational robustness in an RNA virus

“…Also, recent work with bacteriophages has shown that mutational robustness increases the ability to adapt to stressful conditions such as high temperatures (McBride et al. , 2008; Ogbunugafor et al. , 2009).…”