Effects of resource competition and apparent competition on community structure and distributions of drosophilids

点击翻译按钮获取中文摘要

Competitive interactions between drosophilid species are investigated to understand how drosophilid communities are structured and how the boundary of their distributions, especially at lower latitudes are determined. There are two types of competitive interactions, resource competition and apparent competition mediated by organisms of higher trophic level, such as predators. By laboratory experiments on resource competition, it was suggested that intraspecific competition was rather strong in drosophilid species, but interspecific competition was not so strong. The results of field studies did not contradict with this result. Thus, the effects of resource competition on community structure or distribution seem to be weak. On the other hand, cold-tolerant species are expected to be vulnerable to predators or parasitoids, since their locomotor activity is reduced and their developmental period was prolonged, and therefore they may be excluded from warmer regions due to apparent competition with cold-susceptible species. However, little information is available for apparent competition of drosophilids. Then, the species composition, distribution and host association was studied for parasitoids that are assumed to mediate apparent competition. As a result, all parasitoids were able to parasitize a number of host species. Thus, they could mediate interactions between host drosophilid species. In temperate areas, however, the rate of parasitism was not high and there were a period free from parasitism, suggesting that apparent competition was weak. However, there is a possibility that apparent competition is rather severe in subtropical and tropical areas. Further study is needed on this topic.