GENETICS OF DEVELOPMENT TIME IN A BUTTERFLY - PREDICTIONS FROM OPTIMALITY AND A TEST BY SUBSPECIES CROSSING

Earlier studies on adaptive plasticity in development time and diapaus e regulation in the speckled wood butterfly, Pararge aegeria L., have been based on optimality models and have not considered genetics. Neve rtheless, they have been successful in predicting patterns observed. F rom the results of these studies we predicted the genetics of larval a nd pupal development time, as well as of diapause control, to be polyg enic and sex linked. We show that this is the case by crossing a popul ation of the northern subspecies P. a. tircis from southern Sweden, wh ich shows a diapause in some daylengths and is protandrous, with a pop ulation of the southern subspecies P. a. aegeria from Madeira. The lat ter inhabits a much less seasonal environment, develops directly at al l daylengths, and is not protandrous. Offspring showed variable and in termediate larval and pupal development times when reared at daylength s inducing diapause in Swedish pure stock. Female offspring were more similar to their mothers in the reciprocal crosses, whereas developmen t time in male offspring was not sensitive to the direction of the cro ss. This suggests the presence of a sex-linked modifying factor. The r esults show that the outcome of tests of optimality models can be used to predict genetic systems.