Developmental divergence among hatchery strains of rainbow trout (Salmo gairdneri). II. Hybrids

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Abstract
The developmental rates of 1st generation hybrids between 6 closely related hatchery strains of rainbow trout were compared using hatching time, morphology and the pattern of ontogenetic change of 4 enzymes. Hybrid developmental rates cannot be explained by additive genetic effects. Nine of 14 hybrid types developed slower than their maternal parent. These results are consitent with a hypothesis of regulatory divergence between the hybridizing strains. Heterotic effects were observed in 5 hybrid groups in that hybrids developed faster than their maternal parent. A strong dominance component was obsderved in the reciprocal hybrids of one strain. There was no association between the degree of perturbation of hybrid developmental rates and genetic distance between hybridizing strains. Hybrids between more distantly related strains were no more delayed in their development than those from closely related strains.