Antagonistic and reinforcing pleiotropy: a study of differences in development time in wing dimorphic insects

Morphological dimorphisms are found in many different taxa. Wing dimorphism in insects, in which some individuals possess wings and associated flight muscles and are thus volant while others lack a functional flight apparatus and are thus flightless, is a typical example of such types of dimorphisms. It has been extensively studied and such studies have demonstrated that the volant form, although possessing the advantage of flight capability, suffers a fitness cost in a delay in the onset of reproduction after emergence into the adult form and a reduced fecundity. Previous comparative analyses have suggested that there is no consistent trend for development time (hatching to adult) to differ between the two morphs. The present study analyses the phenotypic and genetic correlations between development time and wing morph in the cricket Gryllus firmus . It is shown that the macropterous (volant) morph develops faster than the micropterous (flightless morph). This trade‐off is manifested at both thephenotypic and genetic level. Further, a comparative analysis shows that the same phenotypic trade‐off is generally found in other Orthopteran species so far studied, but in other orders the micropterous morph develops faster. Provided that the phenotypic trade‐off is genetically based, in the Orthoptera the fitness advantage of the earlier onset of reproduction in micropterous females is offset by the extended development time (antagonistic pleiotropy). However, in other orders there is reinforcing pleiotropy in that the micropterous females develop faster and reproduce sooner than the macropterous morph. These results highlight the complexity of fitness interactions and the need to study a phenomenon across several taxa.