Abstract:
The polymorphism of Danaus chrysippus is anomalous since it is a distasteful
butterfly. In a field study of the B locus polymorphism in Ghana, significant
changes in the morph frequencies were recorded over eighteen months at Cape
Coast. There were also significant differences between localities. There was some
evidence that brown morphs are favoured by wet conditions, and that orange
forms have higher survival rates as caterpillars. There were no differences between
forms in larval foodplants, sex ratio, body size, wing damage, mating success,
or in the effects of weather on adult activity. There was however, strong assortative
mating between forms. Crosses with Kenyan females gave aberrant segregations
for the sex chromosomes and the C locus. The results are discussed with regard
to the hypothesis that polymorphism arose as a result of the overlapping of
previously isolated geographical races.
