Wing dimorphism in Gryllus rubens: genetic basis of morph determination and fertility differences between morphs.

The genetic basis of wing morph determination and fertility differences between wing morphs were studied in the wing-dimorphic cricket, Gryllus rubens. Using pair corsses, a significant effect of genotype on morph determination was documented in F progeny of field-collected crickets. The effect of genotype was significantly stronger in females than in males. Results are consistent with an earlier study (Zera and Tiebel 1988) showing that wing development is more strongly buffered from environmental variation in females. Segregation patterns were consistent with a polygenic mode of inheritance and provided no evidence for the existence of genes of major effect, maternal effects, or sex linkage. Only a weak morph x sex association was observed. These results contrast those of Walker (1987) where sex-linked loci of major effect on morph determination were identified in crosses between long-wing and short-wing-selected strains of G. rubens. Short-winged female G. rubens began ovipositing earlier and oviposited significantly more eggs than long-winged females during the first 24 days after adult eclosion. The greater reproductive output of the short-winged morph was due entirely to greater oviposition during the first two weeks after adult eclosion. Preliminary results indicate that flight may further accentuate the reduced reproductive output of long-winged versus short-winged females. These data provide the foundation for investigating the endocrine basis of morph-associated fertility variation in G. rubens and its mechanistic relationship with morph determination.