Effects of temporal priority on the life-history traits of two competing blow fly (Diptera: Calliphoridae) species on carrion

Chrysomya rufifacies is a predaceous introduced species in the western hemisphere, and is suspected to impact the populations of the native blow fly Cochliomyia macellaria. The effects of temporal priority on the survivorship and fitness of C. rufifacies and C. macellaria were investigated in the laboratory. Cochliomyia macellaria arriving within two days of C. rufifacies resulted in a 20-70% reduction in survivorship, pupal weight, and fecundity. Chrysomya rufifacies exhibited a 50% increase in survivorship and fecundity when closely associated temporally with C. macellaria, and was negatively affected by disparate arrival. These results demonstrate C. rufifacies ability to use C. macellaria as a food source, and the positive effect that food source has on C. rufifacies fitness. Temporal priority may allow the competitively weak C. macellaria to persist in a community, while temporal delay appears to benefit C. rufifacies, which exhibits enhanced fitness when acting as a predator in addition to a necrophage. The near 60% reduction in C. macellaria survivorship when in close temporal association with C. rufifacies may be exerting a The 50% increase in survivorship and fecundity exhibited by C. rufifacies when arriving after C. macellaria may be exerting a selective pressure on C. rufifacies to delay colonization despite the risk of an unusable resource. We hypothesize that the window of colonization of carrion by C. macellaria has been restricted due to the establishment of C. rufifacies.