title: Comparing mutational and standing genetic variability for fitness and size in Caenorhabditis briggsae and C. elegans.
abstract: The genetic variation present in a species depends on the interplay between mutation, population size, and natural selection. At mutation-(purifying) selection balance (MSB) in a large population, the standing genetic variance for a trait (VG) is predicted to be proportional to the mutational variance for the trait (VM); VM is proportional to the mutation rate for the trait. The ratio VM/VG predicts the average strength of selection (S) against a new mutation. Here we compare VM and VG for lifetime reproductive success (approximately fitness) and body volume in two species of self-fertilizing rhabditid nematodes, Caenorhabditis briggsae and C. elegans, which the evidence suggests have different mutation rates. Averaged over traits, species, and populations within species, the relationship between VG and VM is quite stable, consistent with the hypothesis that differences among groups in standing variance can be explained by differences in mutational input. The average (homozygous) selection coefficient inferred from VM/VG is a few percent, smaller than typical direct estimates from mutation accumulation (MA) experiments. With one exception, the variance present in a worldwide sample of these species is similar to the variance present within a sample from a single locale. These results are consistent with specieswide MSB and uniform purifying selection, but genetic draft (hitchhiking) is a plausible alternative possibility.
authors: Department of Biology, University of Florida, Gainesville, Florida 32611-8525, USA.
authors: Matthew P
authors: MP
authors: Salomon
authors: Dejerianne
authors: D
authors: Ostrow
authors: Naomi
authors: N
authors: Phillips
authors: Dustin
authors: D
authors: Blanton
authors: Whitney
authors: W
authors: Bour
authors: Thomas E
authors: TE
authors: Keller
authors: Laura
authors: L
authors: Levy
authors: Thamar
authors: T
authors: Sylvestre
authors: Ambuj
authors: A
authors: Upadhyay
authors: Charles F
authors: CF
authors: Baer
mesh_terms: D000465:Algorithms; D000818:Animals; D049628:Body Size / Q000235:genetics; D002107:Caenorhabditis / Q000235:genetics*; D017173:Caenorhabditis elegans / Q000235:genetics*; D005260:Female; D014644:Genetic Variation; D007178:Inbreeding; D008297:Male; D008957:Models, Genetic; D009154:Mutation; D012098:Reproduction / Q000235:genetics; D012641:Selection, Genetic; D013045:Species Specificity