Mechanisms and selection of evolvability: experimental evidence

Abstract

The vast number of species we see around us today, all stemming from a common ancestor, clearly demonstrates the capacity of organisms to adapt to new environments. Understanding the underlying basis of differences in the capacity of genotypes to adapt - that is, their evolvability - has become a major research field. Several mechanisms have been demonstrated to influence evolvability, including differences in mutation rate, mutational robustness, and some kinds of gene interactions. However, the benefits of increased evolvability are indirect, so that the conditions required for selection of evolvability traits are expected to be more limited than for traits that confer immediately beneficial phenotypes. Moreover, just because a trait can affect evolvability does not mean that it actually does so in a particular environment. Instead, some other function of the trait may better explain its success. Nevertheless, there is accumulating experimental evidence that some traits can increase the evolvability of a genotype and that these traits do influence evolutionary outcomes. We discuss recent theory and experiments that demonstrate the potential for traits that influence evolvability to arise and be selected.

Evolutionary tipping points in the capacity to adapt to environmental change

“…In addition, our model indicates that the potential for extinction during tipping point transitions depends critically on the genetic architecture of relevant traits (37) and in particular on the number or magnitude of mutations required to achieve the genotypic optimum for the new selection regime. For example, we expect that populations will be more likely to go extinct when the strategy that needs to be evolved requires either de novo evolution (or loss) of complex organs and structures or a major readjustment of basic physiological/developmental pathways.…”

Biological messiness vs. biological genius: Mechanistic aspects and roles of protein promiscuity

“…An important concept is that the promiscuous intermediates not only provide an opportunity for divergent evolution, but they are also are more easily optimized than specific enzymes to yield new efficient and specific enzymes with a small number of mutations [44–48]. Promiscuous intermediates are highly ‘evolvable’ and it has been suggested that promiscuity is actually selected as an advantageous trait within the entire proteome in order to ensure evolutionary adaptability.…”

Survival and innovation: The role of mutational robustness in evolution

“…Notwithstanding the fact that understanding the link between robustness and selection requires complex mathematical modeling, one can imagine that a population that acquires evolvability as a trait has higher probability of acquiring beneficial mutations and producing offspring with increased fitness. In a scenario in which evolvability, produced by higher robustness, persists long enough in the population as to increase the frequency of individuals with such trait, this trait would be selected favorably because it increases the chances for beneficial mutations to appear in the population [102], a process known as genetic hitchhiking [103]. In the case of duplicated genes, these are likely to return to single gene copies right after duplication, unless they remain in the genome because they increase the mutational robustness of the gene and the evolvability of populations in terms of the emergence of new functions and regulations [104].…”