Community structure and dynamics of fig wasps in syconia of Ficus microcarpa Linn. f. in Fuzhou

Abstract

Ficus microcarpa Linn. f. (Ficus, Moraceae) is a common monoecious tree, which is widely distributed in the fig center area of Asia-Australasia. It is both a main tree species in the tropical forest and a common tree species planted in the courtyard and street. In this study, we investigated the structure, biodiversity and dynamics of fig wasp community in syconia of 19 F. microcarpa plants at two selected sites by observation on and collection from the specific trees at specific time and season all year around. A total of 26,318 fig wasps were collected from 530 syconia in different seasons. Seventeen fig wasp species belonging to Agaonidae, Epichrysomallinae, Otitesellinae, Sycoryctinae, Eurytomidae and Ormyridae of Chalcidoidea were collected. Among them, only Eupristina verticillata of Agaonidae served as a pollinator for F. microcarpa through a way of active pollination. The sex ratio in this pollinating fig wasp species was 0. 16, with a very strong female-bias phenomenon. In the non-pollinators, the sex ratio is higher (0. 46-0. 55) in the species with winged male wasps (Odontofroggatia galili, O. quinifuniculus, O. corneri, Sycophila sp. 1, Sycophila sp. 2 and Meselatus bicolor), lower (0. 31-0. 37) in the species with wingless male wasps (Philotrypesis taiwanensis, Sycoscapter gajimaru, Walkerella microcarpae), and medium (0. 47) in the species with both winged and wingless male wasps (Philotrypesis okinavensis). The results suggested that the sex ratio of fig wasps may be related to the strategy of mating behavior. In the structure of fig wasp community in F. microcarpa, the importance index was dominant in the pollinating fig wasps, but was much smaller in non - pollinating species O. galili and Sycophila sp. 2. According to the number and continuity of occurrence, fig wasps could be classified into common species and occasional species. E. verticillata, Odontofroggatia galili, Walkerella microcarpae, Sycophila sp. 1, Sycophila sp. 2 and Philotrypesis okinavensis were common species, while the remaining 11 were occasional species. The composition and structure of wasp community differed greatly across seasons. From February to June, there were fewer (only 3-4) species inside syconia, with 48. 88 pollinating wasps and 13. 64 non-pollinating wasps in a single fig on average, respectively. From July to January of next year, there were more (as many as 6-13) species inside syconia, with 24. 38 pollinating wasps and 18. 89 non-pollinating wasps in a single fig on average, respectively. The results suggested that the number of pollinating wasps in the latter period reduced greatly compared with that in the former period (P < 0. 001); whereas for the non-pollinating wasps, both the number of species and that of wasps were significantly increased (P = 0. 001). The species and the number of fig wasps in the male-flower phase depended on the species and the number of spawning wasps in the female-flower phase. However, the rainfalls, temperature and the number of syconia in the female-flower phase may affect on the number of spawning wasps and the spawning behavior of wasps. The results of this study provide a scientific basis for urban greening and biodiversity conservation in tropical rain forests.