Genetic architectures of postmating isolation and morphology of two highly diverged rockfishes (genus Sebastes).

This article focuses on the genetic architecture of postmating isolation and morphological divergence between two rockfish species, *Sebastes schlegelii* and *S. trivittatus*, whose reproductive isolation is complete. Using reciprocal backcross populations, the study identified widespread transmission ratio distortion (TRD) across the genome, indicating multifaceted postmating barriers including asymmetric gametic isolation, hybrid inviability involving maternal factors, and extrinsic selection, with some distorted regions coinciding with recombination coldspots. Quantitative trait loci (QTL) mapping revealed significant loci for sex determination—linked to the male-specific gene *amhy*—and morphological traits relevant to speciation and convergence, such as body coloration patterns associated with genes in the melanocortin system (*asip1*, *mc1r*). These findings provide novel insights into the late stages of speciation and phenotypic diversification in non-model marine fishes, highlighting complex genetic and ecological factors maintaining species boundaries.