The Phenotypic Effects of Spontaneous Mutations in Different Environments

Abstract

Understanding the context dependence of mutation represents the current frontier of mutation research. In particular, understanding how traits vary in their abilities to accrue mutational variation and how the environment influences expression of mutant phenotypes yields insight into evolutionary processes. We conducted phenotypic assays in four environments using a set of Daphnia pulex mutation accumulation lines to examine the context dependence of mutation. Life-history traits accrued mutational variance faster than morphological traits when considered in individual environments. Across environments, the mutational variance in plasticity was also greater for life-history traits than for morphological traits, although this pattern was less robust. In addition, the expression of mutational variance depended on the environment, which resulted in changes in the rank order of genotype performance across environments in some cases. Such cryptic genetic variation resulting from mutation may maintain genetic diversity and allow for rapid adaptation in spatially or temporally variable environments.

Fitness change in relation to mutation number in spontaneous mutation accumulation lines ofChlamydomonas reinhardtii

“…It has been proposed that environmental stress might impact the selective effects of mutations and, for example, lead to a release of cryptic genetic variation that cannot be observed under benign conditions (Latta et al 2015). Here, we focused our test on moderately stressful conditions (Kraemer et al 2015), since these conditions represent a more realistic environmental stress than nearly lethal stress.…”

Distributed phenomics with the unPAK project reveals the effects of mutations

“…For example, only 34% of yeast knockout strains show altered fitness phenotypes when grown in rich media, but 97% of strains had phenotypes differing from wild-type in at least one condition when assayed in multiple environments (Winzeler et al, 1999;Giaever et al, 2002;Hillenmeyer et al, 2008). Arabidopsis thaliana traits can be similarly environmentally dependent, and many phenotypes will only be apparent when lines are assayed in a specific environment (K€ ulheim et al, 2002;He et al, 2014;Latta et al, 2015). To the extent that life history and fitness-related characters represent the joint action of many genes and traits across the life cycle, they may be the easiest to detect (Ramani et al, 2012).…”

Mutation accumulation in populations of varying size: large effect mutations cause most mutational decline in the rotifer Brachionus calyciflorus under UV‐C radiation

“…For example, differences in the levels of stress can alter the rate and types of mutations that occur (Bjedov et al, 2003;Wang & Agrawal, 2012;Jiang et al, 2014;Sharp & Agrawal, 2016). Lastly, it is likely that fitness effects measured under laboratory conditions are different than in nature (Agrawal & Whitlock, 2010;Rutter et al, 2012;Yun & Agrawal, 2014;Latta et al, 2015;Stearns & Fenster, 2016). Bearing these caveats in mind, it remains an interesting observation that mutational decline is drastically reduced as population size goes from N = 1 to 20 and that similar patterns have been seen in other systems, and this is consistent with inferences of heavy-tailed distributions made from different approaches.…”

“…Although these results and those of others (Estes et al, 2004;Silander et al, 2007;Katju et al, 2015) inform us of minimum population sizes for avoiding fitness decline in the short term, it is limited in assessing long-term consequences (see above). In addition, measures of fitness in benign laboratory conditions likely underestimate the rate and effect of deleterious mutations in nature (Agrawal & Whitlock, 2010;Rutter et al, 2012;Wang & Agrawal, 2012;Jiang et al, 2014;Latta et al, 2015;Stearns & Fenster, 2016). Understanding the consequences of mutational pressure and assessing conservation concerns awaits estimates of mutational parameters for many more species under different (especially natural) environments.…”