title: Standardizing for microsatellite length in comparisons of genetic diversity.
abstract: Mutation rates at microsatellites tend to increase with the number of repeats of the motif, leading to higher levels of polymorphism at long microsatellites. To standardize levels of diversity when microsatellites differ in size, we investigate the relationship between tract length and variation and provide a formula to adjust allelic richness to a fixed mean number of repeats in the specific case of chloroplast microsatellites. A comparison between 39 loci from eight species of conifers (where chloroplast DNA is paternally inherited) and 64 loci from 12 species of angiosperms (where chloroplast DNA is generally predominantly maternally inherited) indicates that the greater allelic richness found in conifers remains significant after controlling for number of repeats. The approach stresses the advantage of reporting variation in number of repeats instead of relative fragment sizes.
authors.affiliation: UMR Biodiversity, Genes & Ecosystems, Institut National de la Recherche Agronomique, 69 route d Arcachon, F-33612 Cestas cedex, France. petit@pierroton.inra.fr
authors.forename: Rémy J
authors.initials: RJ
authors.lastname: Petit
authors.forename: Marie-France
authors.initials: MF
authors.lastname: Deguilloux
authors.forename: Joëlle
authors.initials: J
authors.lastname: Chat
authors.forename: Delphine
authors.initials: D
authors.lastname: Grivet
authors.forename: Pauline
authors.initials: P
authors.lastname: Garnier-Géré
authors.forename: Giovanni G
authors.initials: GG
authors.lastname: Vendramin
mesh_terms: D018742:DNA, Chloroplast / Q000235:genetics; D005787:Gene Frequency; D014644:Genetic Variation; D019684:Magnoliopsida / Q000235:genetics; D018895:Microsatellite Repeats / Q000235:genetics*; D008957:Models, Genetic; D009154:Mutation / Q000235:genetics; D012044:Regression Analysis; D064028:Tracheophyta / Q000235:genetics
chemical_list: D018742:DNA, Chloroplast