The Oviposition Ecology Of Non-pollinating Fig Wasps And Its Impact Upon The Stability Of Fig-Pollinating Fig Wasps Mutualism

Ficus (Moraceae) and its species-specific pollinator wasps (Agaonidae) form a highly obligate plant-insect mutualistic system, while non-pollinator wasps are exploiters of the system. However, so far, the coexisting mechanism of the exploiter and the mutualistic system still remains unclear. Employing the monoecious Ficus racemosa L. as the material, this article studied the oviposition traits, the diet and the mutual relationships of five non-pollinator wasp species and their impacts on the reproduction of pollinator wasps and figs. These wasp species, parasitic to the fig, include Platyneura testacea Motschulsky, Platyneura mayri Rasplus, Platyneura agraensis Joseph, Apocrypta sp. and Apocrypta westwoodi Grandi. Besides, the oviposition traits of non-pollinator wasps parasitic to Ficus racemosa L. in different seasons and those of non-pollinator wasps parasitic to F. racemosa L. and the dioecious F. hispida L. in the same season were compared respectively. By doing these, it was supposed to gain an insight into the impacts of non-pollinator wasps on the fig-pollinator wasp system and their coexisting mechanism. The results showed as follows:(1) The mean oviposition duration of P. mayri is obviously longer than those of the other four species, and there exist no significant differences among the latter four. The disturbance of ants can shorten the oviposition duration of P.testacea and P. mayri.(2) The oviposition of the five non-pollinator wasp species and the pollinator wasp Ceratosolen fusciceps follows the chronological order: P. testacea, Apocrypta sp., P. mayri, C. fusciceps, A. westwoodi and P. agraensis. The mean oviposition days of P. mayri and A. westwoodi are obviously longer than those of the other three non-pollinator wasp species (n=21, P <0.01), while there exist no significant differences among the latter three species (P>0.05); According to the observation, P. mayri has a larger population of ovipositing wasps than other four non-pollinator wasp species (n=21, P <0.01), while Apocrypta sp. has the smallest (P<0.01); Population sizes of Apocrypta sp. andA. westwoodi respectively show a significant positive correlation with those of P. testacea and P. mayri.(3) Among the five non-pollinator wasp species parasitic to F. racemosa, only P. testacea and P. mayri are gall-makers, who can stimulate the development of ovaries into galls, while the other three species, including Apocrypta sp., A. westwoodi and P. agraensis are parasitoids. The analysis of the natural population of fig wasps revealed that the pollinators are the dominant species, and that Apocrypta sp., A. westwoodi and P. agraensis respectively show a significant positive correlation with P. testacea, P. mayri and C. fusciceps.(4) The oviposition of non-pollinator wasps can obviously increase the number of galls but exerts no significant influence upon the population size of pollinator wasps' offspring and the seed amount.(5) The comparison of the oviposition traits of non-pollinator wasps parasitic to Ficus racemosa L. in two seasons reveals that the oviposition days and population of ovipositing non-pollinator wasps are respectively longer or larger in the foggy and cool season than those in the dry and hot season.(6) The comparison of the oviposition traits of non-pollinator wasps parasitic to Ficus racemosa L. and Ficus hispida L. respectively in the same season shows that the oviposition days and population of ovipositing non-pollinator wasps parasitic to the fomer is longer or larger than those parasitic to the latter.The parasitoids of pollinator wasps and the gall-makers exert negative impacts on the pollinator wasps. However, under the collective influences by ants and parasitoids of the gall-makers, their populations remain on a low level, and thus cannot endanger the dominant status of pollinator wasps. Since their impacts on the stability of the fig-pollinator wasp system are limited, they can coexist with the latter in the long run.Seasonal changes exert a obvious effect on the wasp populations, and its collaboration with non-pollinator wasps may be among the drives behind the fig's evolution from monoecious to dioecious.