Effect of detritus decomposition time on oviposition site selection and developmental success of Aedes aegypti.

The 'oviposition preference-offspring performance' hypothesis (PPH) proposes that females select oviposition sites that optimise offspring performance. For Aedes aegypti L. (Diptera: Culicidae), the main vector of dengue in the Americas, it is expected that females prefer to lay eggs in containers with high nutritional quality, where developmental success is maximised. In this study we aimed to test the PPH in relation to three detritus decomposition time treatments (3, 14 and 42 days). Oviposition was studied during 1 week in three contiguous ovitraps (one per decomposition time treatment) at 18 sites. Immature development in the three treatments was studied at constant densities (20 larvae) or at realistic densities (eggs/treatment in the oviposition study). The number of eggs from the oviposition study and a performance index based on development time, wing length and survival in the immature development study were compared between treatments. Both the oviposition site selection and the subsequent larval development were affected by the detritus decomposition time. Females laid fewer eggs in the 3-day treatment (mean: 16 eggs) than in the 14- and 42-day treatments (mean: 65 and 62 eggs respectively). Immature developmental performance was inversely related to decomposition time at constant densities, and at realistic densities, immatures performed even worse in the longer decomposition time treatments due to higher larval densities. Thus, the effects of detritus decomposition time seem to act in opposite directions for oviposition site selection and immature development success, which does not align with the PPH. One possible explanation for this apparent contradiction is that containers with short detritus decomposition times could indicate a frequent replacement of water, and that females might be selecting signals associated with habitat permanence to ensure the completion of development of their offspring.