Zoology, the Chinese Academy of Sciences, Kunming, Yunnan 650223, China 2. Sciences, Northwest University, Xi'an, Shaanxi 710069, China 3. Xishuangbanna Tropical Botanical Garden, the Chinese Academy of Sciences, Kunming, Yunnan 650223, China
Ficus (Moraceae) and their species-specific pollinator wasps (Agaonidae) form a remarkable plant-insect obligate mutualism, and non-pollinators are the exploiters of the mutualism. The negative impact of exploiters on the reciprocal mutualists might disrupt the reciprocal mutualism in the process of evolution, but how the exploiters could coexist with the reciprocal mutualsits is not still clear. In this study, the diet of the five species of non-pollinators and relationship among fig wasps were analyzed on Ficus racemosa L. in Xishuangbanna from Dec. 2003 to Apr. 2004. In a controlled experiment pollinators and each species of non-pollinators oviposited and counts of wasps and seeds in mature figs were conducted. The results indicated that only Platyneura testacea Motschulsky and Platyneura mayri Rasplus are gall-makers, which can induce the ovaries into galls; Apocrypta sp., Apocrypta westwoodi Grandi and Platyneura agraensis Joseph are the parasitoids. The gall-makers and the parasitoids of pollinators have negative impacts on pollinators, but the impacts are not significant because of the influence of the ants and parasitoids of gall-makers. Additionally, the experiment excluding non-pollinators oviposition showed that the number of offspring of pollinators and seeds were not significantly different with the natural fruits. Moreover, the analysis on the natural population structure of fig wasps revealed that the pollinators are the dominant species. So in the natural condition, the abundance of gall-makers and parasitoids of pollinators are below the level needed to exclude pollinators, and thus they have a relatively weak impact on the stability of fig-pollinator mutualism and can coexist with the mutualism.