Heterosis and maternal effects in salinity tolerance of the guppy Poecilia reticulata

Salinity response in F sub(1) hybrids of the guppy was measured as survival time after subjecting mature fish to 35 ppt artificial seawater. The amount of heterosis was expressed by the difference between the means of the F sub(1) hybrids and the parental strains. The mean survival times of the F sub(1) hybrids were higher than the mid-parent values, indicating heterosis. The amount of heterosis differed among strain combinations. A positiye correlation was observed between the survival times of the F sub(1) hybrids and the female parents but not between the F sub(1) hybrids and the male parents, indicating maternal effects. These results suggest that the heterosis observed in the F sub(1) hybrids is attributable to two components: the first is the non-maternal component induced by strain combinations and the second is the maternal effects of strain populations.