EFFECTS OF TEMPORAL PRIORITY ON INTERSPECIFIC INTERACTIONS AND COMMUNITY-DEVELOPMENT

The effects of temporal priority on interactions between the larvae of Drosophila hydei and D. melanogaster were investigated experimentally in the laboratory. In general, the species which arrived first at the resource had a competitive advantage, the extent of which was related to the length of the temporal separation between species introduction . A small or moderate temporal priority for one species tended to prod uce an unreciprocated inhibitory effect in the other and thus the inte raction which occurred was highly asymmetric (amensal). However, if a species arrived very late at the resource it performed better if the r esource had been previously utilized by larvae of the other species. T his was due to amelioration of otherwise harsh conditions by the early -arriving larvae. Therefore, temporal priority can influence the direc tion, form and intensity of the interaction which occurs between two s pecies. Due to the competitive advantage obtained when arriving first, competitively weak species may be able to persist in a community if t hey attain temporal priority on at least some patches of resource. How ever, in harsh conditions, arriving after another species may have pos itive effects due to a reduction in environmental stresses. The effect s of temporal priority on interspecific interactions are therefore con sidered to be an important factor in the structuring of ecological com munities.