Elevated mutation rates are unlikely to evolve in sexual species, not even under rapid environmental change

Abstract

Background Organisms are expected to respond to changing environmental conditions through local adaptation, range shift or local extinction. The process of local adaptation can occur by genetic changes or phenotypic plasticity, and becomes especially relevant when dispersal abilities or possibilities are somehow constrained. For genetic changes to occur, mutations are the ultimate source of variation and the mutation rate in terms of a mutator locus can be subject to evolutionary change. Recent findings suggest that the evolution of the mutation rate in a sexual species can advance invasion speed and promote adaptation to novel environmental conditions. Following this idea, this work uses an individual-based model approach to investigate if the mutation rate can also evolve in a sexual species experiencing different conditions of directional climate change, under different scenarios of colored stochastic environmental noise, probability of recombination and of beneficial mutations. The color of the noise mimicked investigating the evolutionary dynamics of the mutation rate in different habitats. Results The results suggest that the mutation rate in a sexual species experiencing directional climate change scenarios can evolve and reach relatively high values mainly under conditions of complete linkage of the mutator locus and the adaptation locus. In contrast, when they are unlinked, the mutation rate can slightly increase only under scenarios where at least 50% of arising mutations are beneficial and the rate of environmental change is relatively fast. This result is robust under different scenarios of stochastic environmental noise, which supports the observation of no systematic variation in the mutation rate among organisms experiencing different habitats. Conclusions Given that 50% beneficial mutations may be an unrealistic assumption, and that recombination is ubiquitous in sexual species, the evolution of an elevated mutation rate in a sexual species experiencing directional climate change might be rather unlikely. Furthermore, when the percentage of beneficial mutations and the population size are small, sexual species (especially multicellular ones) producing few offspring may be expected to react to changing environments not by adaptive genetic change, but mainly through plasticity. Without the ability for a plastic response, such species may become – at least locally – extinct. Electronic supplementary material The online version of this article (10.1186/s12862-019-1494-0) contains supplementary material, which is available to authorized users.

In silicoexperiments uncover a novel mechanism underlying mutation rate evolution in sexually reproducing populations

“…Clonally reproducing organisms, such as bacteria, have been shown to evolve higher MR when mutator alleles are genetically linked with traits providing higher fitness (14, 16). In sexually reproducing organisms, genetic recombination is capable of effectively separating mutator alleles from adaptive alleles, which is the primary reason it is believed that selection for higher MR is not possible in populations with sexual reproduction (13, 26, 27). Our results presented so far indicate that selection for higher MR is still possible even in the presence of genetic recombination.…”

Genetic architecture of dispersal and local adaptation drives accelerating range expansions

“…They find that the rate of adaptation at the range front increases because of the evolution of increased mutation rates encoded by a modifier locus. For sexual species, this result can be sensitive to the assumed distribution of mutation effects and level of linkage between the modifier locus and local adaptation locus because the modifier locus evolves by hitch-hiking [46]. However, in our model, there is no need for evolution at a modifier locus.…”

Adaptive and nonadaptive plasticity in changing environments: Implications for sexual species with different life history strategies

“…Reliability of sensing, that is, the correlation between sensed environmental cues and environmental variables affecting fitness, has been investigated by Reed et al (2010), Ashander et al (2016), and Ergon and Ergon (2016), but was beyond the scope of our work. The value of the mutation rate was picked according to results of a simulation model on the evolution of the mutation rate after 300 generations of a population experiencing stochastic environmental conditions (no climate change, and no plasticity, Romero-Mujalli et al, 2019a). In addition, this value is within the range of mutation rates used in other simulation models (reviewed in Romero-Mujalli et al, 2019b).…”

“…Simulation experiments were also evaluated under scenarios of lower mutation rate, and mutational effects according to the model of slightly deleterious mutations (Eyre-Walker et al, 2002;Ohta, 1973;Romero-Mujalli et al, 2019a), which imposed higher genetic constraints. The analysis of data and plotting was performed in r v3.5.2.…”