MIGRATION RATES, FREQUENCY-DEPENDENT SELECTION AND THE SELF-INCOMPATIBILITY LOCUS IN LEAVENWORTHIA (BRASSICACEAE)

• Published in: Evolution Vol. 65; no. 8; pp. 2357 - 2369
• Main Authors: Joly, Simon, Schoen, Daniel J.
• Format: Journal Article
• Language: English
• Published: Malden, USA Blackwell Publishing Inc 01.08.2011; Wiley Subscription Services, Inc; Oxford University Press
• Subjects: Animal migration; Animal migration behavior; Balancing selection; Bayesian analysis; Biological Evolution; Brassicaceae - genetics; Brassicaceae - physiology; divergence time estimates; Ecosystem; Evolution; Evolutionary genetics; Gene Flow; Gene loci; Genetic loci; Genetic mutation; Genetic Variation; Genetics, Population; Maximum likelihood method; Models, Genetic; Parametric models; Plant species; Population estimates; Population migration; Population size; Population structure; Selection, Genetic; self-incompatibility locus
• ISSN: 0014-3820; 1558-5646; 1558-5646
• DOI: 10.1111/j.1558-5646.2011.01300.x

Loci subject to negative frequency-dependent selection are expected to exhibit higher effective migration rates compared to reference loci. Although the number of gene copies transferred between populations by migration is the same for all genes, those subject to negative frequency-dependent selection are more likely to be retained in the immigrant population because rare alleles are selectively favored. So far, evidence for this prediction has been indirect, based on summary statistics rather than on migration rate estimates. Here, we introduce an approximate Bayesian procedure to jointly estimate migration rates at two predefined sets of loci between two populations. We applied the procedure to compare migration rate estimates at the self-incompatibility locus (S-locus) with that at 10 reference loci in two plant species, Leavenworthia alabamica and L crassa (Brassicaceae). The maximum likelihood estimate for the proportion of migrants (m) was four times higher at the S-locus than at reference loci, but the difference was not statistically significant. Lack of significance might be due to insufficient data, but perhaps also to the recent divergence of the two species (311 ka), because we also show using simulations that the effective migration rate at the S-locus is expected to increase with increasing divergence time. These findings aid in understanding the evolutionary dynamics of negative frequency dependent selection and they suggest that divergence time should be accounted for when employing migration rates to help detect negative frequency-dependent selection.