MBE Advance Access originally published online on December 23, 2008
Molecular Biology and Evolution 2009 26(3):659-669; doi:10.1093/molbev/msn287
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Research Articles |
Spontaneous Mutational and Standing Genetic (Co)variation at Dinucleotide Microsatellites in Caenorhabditis briggsae and Caenorhabditis elegans
Department of Zoology, University of Florida
E-mail: cbaer{at}ufl.edu.
Accepted for publication December 10, 2008.
Understanding the evolutionary processes responsible for shaping genetic variation within and between species requires separating the effects of mutation and selection. Differences between the patterns of genetic variation observed in nature and when mutations are allowed to accumulate in the relative absence of selection can reveal biases imposed by selection. We characterize the genetic variation at dinucleotide microsatellite repeats in four sets of 250-generation mutation accumulation (MA) lines, two in the species Caenorhabditis briggsae and two in Caenorhabditis elegans, and compare the mutational variation with the standing variation in those species. We also compare the mutational properties of microsatellites with the cumulative effects of mutations on fitness in the same lines. Integrated over the whole genome, we infer that the mutation rate of C. briggsae is about twice that of C. elegans, consistent with the cumulative mutational effects on fitness. The mutational spectrum (ratio of insertions to deletions) differs between repeat types and, in some cases, between species. The per-locus mutation rate is significantly positively correlated with the standing genetic variation at the same locus in both species, providing justification for the common practice of using the standing genetic variance as a surrogate for the mutation rate.
Key Words: heterozygosity • microsatellite • mutation accumulation • mutational variance • spontaneous mutation • tandem repeat
1 These authors contributed equally.
2 Present address: Department of Biology, Arcadia University, Glenside, PA.
Diethard Tautz, Associate Editor
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