DIFFERENTIAL RESOURCE CONSUMPTION OBVIATES A POTENTIAL FLIGHT FECUNDITY TRADE-OFF IN THE SAND CRICKET (GRYLLUS-FIRMUS)

1. The physiological basis of life-history trade-offs is poorly unders tood. A useful system in which the underlying physiological mechanisms can be studied is wing polymorphism in insects. 2. The sand cricket, Gryllus firmus (Orthoptera, Gryllidae), exists in natural populations as either a fully-winged (LW), flight-capable morph or a short-winged (SW) morph that cannot fly. 3. We characterized the morphs with respec t to physiological features that influence a potential trade-off betwe en flight capability and fecundity. We measured nutritional indices, f light muscle development and ovarian development in the LW and SW morp hs. 4. In adults, ovarian growth occurred after the completion of flig ht muscle growth which precludes a direct trade-off of resources devot ed to the growth of these two organs. 5. In feeding trials with adult female crickets, the efficiency with which assimilated nutrients were converted to new tissue growth was significantly lower in LW vs SW mor phs. This result is consistent with the existence of a metabolic cost resulting from the maintenance of the large flight muscles in the LW m orph, which are not present in the SW morph. 6. Despite this reduced e fficiency, total biomass gain, ovarian growth and the number of eggs o viposited did not differ between morphs. This was the result of increa sed food acquisition by LW vs SW females in these trials, in which cri ckets were fed a nutritious diet ad libitum. 7. The LW morph of G. fir mus can counter the energetic demands of flight capability by consumin g additional food and thus can avoid a cost in terms of reduced fecund ity and so obviate the trade-off. 8. Trade-offs may be generally obvia ted when neither environmental supply nor the organismal processes of digestion and absorption limit resource availability.