title: Cryptic population genetic structure: the number of inferred clusters depends on sample size.
abstract: Clustering methods have been used extensively to unravel cryptic population genetic structure. We investigated the effect of the number of individuals sampled in each location on the resulting number of clusters. Our study was motivated by recent results in Arabidopsis thaliana: studies in which more than one individual was sampled per location apparently have led to a much higher number of clusters than studies where only one individual was sampled in each location, as is generally done in this species. We show, using computer simulations and microsatellite data in A. thaliana, that the number of sampled individuals indeed has a strong impact on the number of resulting clusters. This effect is smaller if the sampled populations have a hierarchical structure. In most cases, sampling 5-10 individuals per population should be enough. The results argue for abandoning the concept of 'accessions' in partially selfing organisms.
authors.affiliation: Evolutionary Functional Genomics, Department of Evolution, Genomics and Systematics, Uppsala University, Norbyvägen 18 D, SE-752 36 Uppsala, Sweden Department of Biology, University of Oulu, 90014 Oulu, Finland Plant Ecology, Department of Ecology and Evolution, Uppsala University, Villavägen 14, SE-752 36 Uppsala, Sweden.
authors.forename: Johan
authors.initials: J
authors.lastname: Fogelqvist
authors.forename: Anne
authors.initials: A
authors.lastname: Niittyvuopio
authors.forename: Jon
authors.initials: J
authors.lastname: Agren
authors.forename: Outi
authors.initials: O
authors.lastname: Savolainen
authors.forename: Martin
authors.initials: M
authors.lastname: Lascoux