POPULATION AGGREGATION FACILITATES COEXISTENCE OF MANY COMPETING CARRION FLY SPECIES

We studied experimentally the effect of resource subdivision and popul ation aggregation on the number of coexisting species in the coexistin g species in the community of carrion flies. Placing small pieces of c ow liver (50 g) in a cultivated field we created a homogeneous but pat chy environment for the ovipositing flies. For the larval development, two or four pieces of liver were combined to a single unit to remove resource patchiness during larval competition.This manipulation increa sed interspecific aggregation but decreased intraspecific aggregation. The size of the emerging flies, which reflects the level of competiti on, varied more between rearings when patchiness was retained. These r esults imply greater spatial variation in intraspecific competition in the more patchy environment. Combining four pieces of resource into a single unit led to a clear reduction in the number of emerging specie s, and a clear increase in the dominance of the most abundant species, compared with a control group. Our results strongly support the notio n that independent aggregation of competitors facilitates their coexis tence, and hence regional diversity.