A Life History Trade-Off in Drosophila Species and Community Structure in Variable Environments

1. Within taxa at the class or family level, the developmental period is often proportional to adult life span. In Drosophila species, a short developmental period increases larval competitive ability. Species with a long adult life, however, may have a better chance to reach new breeding sites in time and space. In another paper (Sevenster & Van Alphen 1993), we presented a model incorporating this trade-off. It shows that fast larval developers (`fast species') are dominant when breeding opportunities are frequent, and that good adult survivors (`slow species') are dominant when breeding opportunities are scarce. Moreover, the model demonstrates that a fast and a slow species may coexist in intermediate environments. In this paper we show that data from experiments and the field support the model. 2. The trade-off between larval developmental rate and adult survival is established in a guild of frugivorous Drosophila species from Panama. 3. The interval between provisioning with larval food in population cages influences the outcome of competition between a fast and a slow species roughly as predicted by the model. 4. In the field, slow species are more abundant among adults than among recruits, as is expected from differential survival of adults and from differential competitive ability of larvae. 5. The guild composition in the field shifts towards fast species when fruits are abundant, and towards slow species when fruits are scarce. 6. Specialized species, which perceive a lower abundance of breeding sites than generalists, are slower species than are the generalists. 7. We conclude that there is ample evidence that differences in life-history strategy influence the structure of natural communities in a predictable way and promote the coexistence of species using similar resources.