The maintenance of self-incompatibility: overdominance of inbreeding depression and S-linked genetic load

Abstract

O_LIInbreeding 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. C_LIO_LIBayesian 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. C_LIO_LIThere 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. C_LIO_LIThe 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. C_LI