A Trait‐based framework for mutation bias as a driver of long‐term evolutionary trends

Abstract

Previous work has shown that mutation bias can direct evolutionary trends in genotypic space under strong selection and rare mutation. We present an extension of this work to general traits of the organism. We do this by allowing many different genotypes, with different fitnesses, to have the same trait value. This approach makes novel predictions and shows that the outcome of evolution for a trait is influenced by mutation bias as well as the fitness distribution of the genotypes that have the same trait value. This distribution can alter evolution in interesting ways, depending on the likelihood of generating high fitness mutants. We also show that mutation bias can direct evolution when many mutants are present at any one time. We demonstrate that mutation bias can drive longterm evolutionary trends when the environment is constantly changing. Under biologically realistic conditions, we show that mutation bias can counter strong gradients of environmental selection over time. We conclude that evolutionary trends can be quite independent of the environment, even when they depress population fitness. Finally, we show that entropy can be a powerful source of mutation bias and can drive evolutionary trends. V C 2015 Wiley Periodicals, Inc. Complexity 21: [331][332][333][334][335][336][337][338][339][340][341][342][343][344][345] 2016

How does mutation affect the distribution of phenotypes?

“…Although the contribution of the distribution of standing genetic variance has been considered from a variety of perspectives (e.g., Blows and Hoffmann 2005;Estes and Arnold 2007;Futuyma 2010;Losos 2011), the potential role of mutation in determining patterns of phenotypic evolution, particularly on complex, multipeak adaptive landscapes, warrants further attention (Tanaka 1998;Arthur 2004;Losos 2011;Xue et al 2016;Houle et al 2017). Although the contribution of the distribution of standing genetic variance has been considered from a variety of perspectives (e.g., Blows and Hoffmann 2005;Estes and Arnold 2007;Futuyma 2010;Losos 2011), the potential role of mutation in determining patterns of phenotypic evolution, particularly on complex, multipeak adaptive landscapes, warrants further attention (Tanaka 1998;Arthur 2004;Losos 2011;Xue et al 2016;Houle et al 2017).…”

“…The causes of evolutionary patterns of phenotypic diversification and stasis have long occupied biologists. Although the contribution of the distribution of standing genetic variance has been considered from a variety of perspectives (e.g., Blows and Hoffmann 2005;Estes and Arnold 2007;Futuyma 2010;Losos 2011), the potential role of mutation in determining patterns of phenotypic evolution, particularly on complex, multipeak adaptive landscapes, warrants further attention (Tanaka 1998;Arthur 2004;Losos 2011;Xue et al 2016;Houle et al 2017). Mutation is typically considered a random process, occurring at sufficient frequency to support evolution via the maintenance of standing genetic variance.…”

Supply-driven evolution explains the locking-in of structures that open new evolutionary possibilities, such as higher hierarchies of organization

“…Alternative approaches include a simpler but crude model for thinking about mutation bias (Xue et al, 2015) based on the concept whereby two organisms with same trait value do not necessarily have the same fitness. As observed by Arthur (2001), changes in a trait value such as body length can be achieved via different developmental mechanisms such as increased cell size or cell proliferation.…”

“…We define an NK model that is similar to, but different from, the model described in Xue et al (2015). Agents are now strings of L bits, either 0 or 1.…”

“…An alternative approach consists in considering the probabilistic nature of the relationship between trait values and fitness: two organisms with the same trait value do not necessarily have the same fitness [27]. This is because changes in a trait value such as body length can be achieved via different mechanisms, such as increased cell size or cell proliferation [28].…”