Genomic mutation rates for lifetime reproductive output and lifespan in Caenorhabditis elegans.

Theory concerning the evolution of sex and recombination and mutation load relies on information on rates and distributions of effects of deleterious mutations. Direct information on the genomic mutation rate in Drosophila implies that an accumulation of mildly deleterious mutations reduces viability of populations by at least 1% per generation. We carried out an experiment to measure the deleterious mutation rate in Caenorhabditis elegans, in which independent sublines were maintained with one hermaphrodite parent per generation, conditions that minimize the opportunity for natural selection and lead to random fixation of deleterious mutations. After 60 generations of mutation accumulation, negligible changes in mean reproductive output and lifespan occurred, but the genetic variance increased at rates typical for life history traits in other species. The estimated deleterious mutation rate per haploid genome for fitness, U, was 0.0026, a figure two orders of magnitude smaller than previously measured for viability in Drosophila.