Hybridization is a source of phenotypic novelty and variation. While researchers have acknowledged additive genetic variation through chromosomal recombination, the roles of non-additive inheritance in shaping phenotypic distribution have been underappreciated. Here, we explored phenotypic distribution of F1 hybrids by a meta-analysis based on 39 species pairs across male animals. Additive inheritance will restrict F1 hybrids phenotypic distribution to the intermediate between parental species.
Generally, phenotypic distribution of F1 hybrids resembled mothers (maternal effect). We further show that non-additive interactions, which is shaped by divergence between parental species, are a powerful source of phenotypic novelty and variation – hybrids expressed novel phenotype in 65% of species pairs, and larger variation than parentals in 25% of traits. Genetic divergence did not affect the probability of novel phenotype expression but reduced trait value (outbreeding depression). Phenotypic/genetic divergence between parental species increased variation of F1 hybrids, presumably because of damaged developmental stability.
Since sex-specific genome elements have limited impact on phenotypic distribution, observed patterns in male-specific traits may also appear in other traits including sexually monomorphic traits. By providing novel phenotype and increasing phenotypic variation, non-additive allelic interactions may play key roles in determining ecological/mating success of F1 hybrids.