A new model of lateral plate morph inheritance in the threespine stickleback,Gasterosteus aculeatus.

The threespine stickleback,Gasterosteus aculeatus, is polymorphic for the arrangement of lateral bony plates. It is confirmed in this paper that four morphs (not three) should be distinguished in this species: low plated, low plated with a keel, partially plated and completely plated. A new model is proposed to explain the inheritance of these morphs which involves one major gene with three alleles displaying a dominance hierarchy withA (completely plated) dominant toa (low plated) which is dominant toa k (low plated with keel). The dominance of theA allele is modified to semidominance by a dominant alleleC at a second locus. This scheme explains all the results of relevant breeding experiments published so far. Field data also fulfill predictions derived from this model.