The maintenance of self-incompatibility and the genetic architecture of inbreeding depression

Abstract

SummaryInbreeding depression plays a fundamental role in evolution. To help detect and characterize viability loci that underlie inbreeding depression, we forced self-pollinated plants from self-incompatible populations of Leavenworthia alabamica to produce families of progeny that were genotyped at hundreds of mapped single nucleotide polymorphism (SNP) loci.Bayesian analysis of segregation data for each SNP was used to explore support for different dominance and selection coefficients at linked viability loci in different genomic regions.There was some support for overdominance (or pseudo-overdominance) at a few viability loci, as well as for recessiveness and underdominance. One recessive viability locus mapped to the genomic region of the novel self-incompatibility locus in Leavenworthia alabamica, but in general there was no support for strongly recessive viability loci of major effect.The results are consistent with earlier findings showing that inbreeding depression is recalcitrant to purging in Leavenworthia alabamica. The results also help account for the maintenance of self-incompatibility in this species and are consistent with expectations from evolutionary genetic theory that recessive, deleterious alleles linked to loci under balancing selection are sheltered from selection.