Role of saprophagous fly biodiversity in ecological processes and urban ecosystem services

1. Direct consumption of organic matter by the saprophagous larvae provides the ecosystem with a fundamental service by recycling nutrients and reducing exposure to decomposing matter. The present study aimed to assess the functional role of saprophagous flies in the mass loss of different types of decomposing organic matter. 2. Two types of common urban waste were used to measure the role of flies in reducing organic matter: chicken viscera (chicken) and a mixture of flour and uncooked eggs (flour and eggs), representing leftover food. Ten traps baited with each substrate, under field conditions, allowed fly access (exposed to flies) and three traps from each substrate did not (unexposed controls); adult flies entering the traps or emerging from the substrates and substrate mass loss were recorded. 3. Species from Calliphoridae, Sarcophagidae, Muscidae, and Fanniidae families were collected mainly in traps baited with chicken, with Phoridae being the most abundant in traps with flour and eggs as bait. A significantly richer (P < 0.05) assemblage of fly species accessed the traps baited with chicken viscera (21 species) compared with those emerging (11 species), whereas similar numbers of species accessed (n = 5) or emerged (n = 1) from traps baited with flour and eggs (average richness accessing 7.97, emerging 2.83). Chicken substrate mass loss and species richness were positively related (r = 0.56, P = 0.001). In traps where richness was larger than 10 species, the substrates were reduced by more than 85% of their initial weight compared with unexposed controls, which lost 30%. Substrate mass loss significantly increased with the abundance of flies (r = 0.73, P < 0.0001). 4. The results of the present study support the functional role of saprophagous species diversity on the decomposition rates of organic matter, reinforcing the negative consequences of loss or gain of species in modified landscapes and for ecosystem function.