Genetic Determination of Offspring Size in the Guppy (Poecilia reticulata)

Abstract

Interpopulation differences in offspring size of guppies are closely associated with interpopulation differences in predation on guppies. In some ovoviviparous fish offspring size is determined by the genotype of the mother. The paternal (P1) genome made no contribution to F1 offspring size but, in contributing to the F1 female genotype, helped to determine the size of the F2 offspring. This delayed inheritance was named the grandfather effect. Because guppies also appear to be ovoviviparous, they should display a similar grandfather effect. Since the experiments involved the hybridization of guppies from different localities, they potentially demonstrate a genetic basis for the interpopulation differences in offspring size.