REPRODUCTIVE COMPONENTS OF FICUS HISPIDA AND ITS POLLINATOR

Abstract

The interaction between Ficus species and their pollinating wasps (Agaonidae) represents a striking example of mutualism. With few exceptions, seed production by fig trees is dependent on a unique fig-pollinating wasp, and the pollinator's offspring feed only on the ovules. We studied the reproductive components of Ficus hispida and its pollinator (Ceratosolen solmsi marchali) in the tropical area of Xishuangbanna. Ficus hispida is functionally dioecious, with male and female functions relegated to separate plants, called gall and seed figs. Gall figs are functionally male because they foster the pollinator larvae that disperse the fig's pollen as adults. Seed figs are functionally female and produce only seeds. When a syconium becomes receptive, pollinators will enter it and lay eggs or pollinate the female flowers inside the syconium cavity. The pollinators trapped inside the syconium cavity and in the ostiole were recorded in the wild. The results showed that mean foundress number was greater in female than in male syconia (females: 2.72±2.04; males: 2.08±1.65). About 52% of the foundresses could enter the cavity of the female syconia through the ostiole and only 35% for the male syconia. Many foundresses died in the ostiole and consequently failed to lay eggs and pollinate the female syconium. As there were fewer female flowers per syconium in male than in female syconia, and foundress numbers were greater in female than in male syconia, female syconia produced more seeds than male syconia produced pollinators, and the number of seeds (1 891.63 ± 471.53) was over five times of the number of pollinators (367.20 ± 208.02). In female syconia, there was a significant positive correlation between seeds and female flowers, while there was a significant negative correlation between the number of seeds and aborted female flowers. Male syconia produced pollen and wasps also reproduced inside the male syconia, but many factors influenced pollinator reproduction. Gall numbers showed the strongest impact on the pollinator population; the secondary factor was aborted galls, which could reduce the pollinator numbers by about 30%; the third factor was the total number of female flowers, which influenced the oviposition ratio of pollinators. Moreover, three species of non-pollinating wasps, Philotrypesis pilosa, Philotrypesis sp., and Apocrypta bakeri, oviposit from outside the syconium into ovaries containing pollinator eggs on the male tree. They co-existed with pollinators inside the male syconia. The non-pollinating wasps had a direct impact on the reproductive success of the pollinator wasp and were able to reduce the number of pollinator individuals per male syconium by 30. They also showed an indirect impact on the host figs.