Carrion fly community dynamics: patchiness, seasonality and coexistence

ABSTRACT. 1. An outdoor cage experiment was conducted to test the theory that localized interactions facilitate coexistence of species breeding in ephemeral habitats. The same amount of larval resource (50 g of liver) but divided into one, two, four, eight or sixteen pieces was placed into each of fifteen cages once a week from June to September for 4 years. 2. The cage populations were initially mixtures of thirteen species but after 4 years only Lucilia illustris (Meig.), Sarcophaga scoparia Pand. and S.aratrix Pand. remained. Lucilia illustris , by far the most abundant species in the field, predominated in every cage. 3. Sarcophaga went extinct in most cages, but they survived in five cages in which the larval resource was much divided, in agreement with the theoretical prediction. 4. Lucilia silvarum (Meig.) emerged about a week later than L.illustris in early summer; this phenological difference gave rise to a competitive asymmetry between the two species. This difference appears to explain why L.silvarum went extinct in the cages in 3 years, and it may explain why L.silvarum has consistently been less abundant than L.illustris in the natural community. 5. Other differences in phenology, voltinism and rate of development in the flies are described, and such differences are suggested to facilitate regional coexistence of many species in seasonal environments.