Fitness decline in spontaneous mutation accumulation lines of Caenorhabditis elegans with varying effective population sizes

  • Vaishali Katju (Creator)
  • Lucille B. Packard (Creator)
  • Lijing Bu (Creator)
  • Peter Keightley (Creator)
  • Ulfar Bergthorsson (Creator)



Productivity and survivorship to adulthood for MA lines following 100 consecutive generations of mutation accumulation and the ancestral controls. Column 1 corresponds to the line identifier (MA line or ancestral control line). Column 2 lists the replicate number for each line (where possible, we aimed for five replicates within each line). Columns 3-10 list the worm productivity corresponding to Days 1-8 of the productivity assay. Column 11 is the total productivity summed across Days 1-8. Column 12 lists the number of surviving adults from a pool of L1 larvae initially isolated. Column 13 is the final value for survivorship to adulthood and ranges from 0 to 1 (corresponding to 0 to 100% survivorship to adulthood). Dashes in cells represent lack of data due to hermaphrodite mortality during the assay or inability to enter the replicate line into assay due to sterility or mortality in preceding generations.


The rate and fitness effects of new mutations have been investigated by mutation accumulation (MA) experiments in which organisms are maintained at a constant minimal population size to facilitate the accumulation of mutations with minimal efficacy of selection. We evolved 35 MA lines of Caenorhabditis elegans in parallel for 409 generations at three population sizes (N = 1, 10, and 100), representing the first spontaneous long-term MA experiment at varying population sizes with corresponding differences in the efficacy of selection. Productivity and survivorship in the N = 1 lines declined by 44% and 12%, respectively. The average effects of deleterious mutations in N = 1 lines are estimated to be 16.4% for productivity and 11.8% for survivorship. Larger populations (N = 10 and 100) did not suffer a significant decline in fitness traits despite a lengthy and sustained regime of consecutive bottlenecks exceeding 400 generations. Together, these results suggest that fitness decline in very small populations is dominated by mutations with large deleterious effects. It is possible that the MA lines at larger population sizes contain a load of cryptic deleterious mutations of small to moderate effects that would be revealed in more challenging environments.

Data Citation

Katju V, Packard LB, Bu L, Keightley PD, Bergthorsson U (2014) Data from: Fitness decline in spontaneous mutation accumulation lines of Caenorhabditis elegans with varying effective population sizes. Dryad Digital Repository.
Date made available15 Oct 2014

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