Papers in the Biological Sciences


Date of this Version

June 1994


Published in Functional Ecology 8 (1994), pp. 573–580. Copyright © 1994 S. Mole and A. J. Zera; journal compilation © 1994 British Ecological Society; published by Blackwell Publishing. Used by permission.


1. The physiological basis of life-history trade-offs is poorly understood. 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 as a short-winged (SW) morph that cannot fly.
3. We characterized the morphs with respect to physiological features that influence a potential trade-off between flight capability and fecundity. We measured nutritional indices, flight muscle development and ovarian development in the LW and SW morphs.
4. In adults, ovarian growth occurred after the completion of flight muscle growth which precludes a direct trade-off of resources devoted 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 morphs. This result is consistent with the existence of a metabolic cost resulting from the maintenance of the large flight muscles in the LW morph, which are not present in the SW morph.
6. Despite this reduced efficiency, total biomass gain, ovarian growth and the number of eggs oviposited did not differ between morphs. This was the result of increased food acquisition by LW vs SW females in these trials, in which crickets were fed a nutritious diet ad libitum.
7. The LW morph of G. firmus can counter the energetic demands of flight capability by consuming additional food and thus can avoid a cost in terms of reduced fecundity and so obviate the trade-off.
8. Trade-offs may be generally obviated when neither environmental supply nor the organismal processes of digestion and absorption limit resource availability.

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