Factors influencing populations of the fig pollinator (Liporrhopalum tentacularis) and its parasitoid (Sycoscapter sp.)

Abstract

In this thesis, I investigate factors affecting the ecology and evolution of the dioecious fig Ficus montana, its pollinator Liporrhopalum tentacularis and the non-pollinating fig wasp Sycoscapter sp. E montana grows naturally in soils of varying nutrient quality. Under experimental conditions, with enhanced soil nutrition, both female and male plants responded in the same way, producing more leaves, stems and many more figs, but in female plants the figs were also larger, and produced more seeds. In male plants the size of the figs remained unaltered. Female figs that contained more flowers produced more seeds, but male figs that produced more flowers did not produce more female pollinators. Although the female pollinators laid more eggs in figs with more flowers, the number of female pollinators was differentially reduced by Sycoscapter and other factors, cancelling out any male fig size effect. The timing and frequency of foundress re-emergence from male and female figs was similar. Foundresses first started to re-emerge from figs of both sexes after about one hour and after an over-night halt, keep on emerging through to the next day. Using a novel poisoning technique the rates of oviposition and pollination were found to be rapid when the wasps first entered, but declined rapidly in both male and female figs. The likelihood of foundresses re-emerging from male figs was not influenced by wasp age, flower number, or the timing of entry into the figs, but re-emergence was more frequent from older figs. Foundresses laid most of their male eggs early in an oviposition bout. The responses of winged and wingless foundresses to varying foundress numbers were different, because the wingless foundresses laid smaller clutches that were independent of foundress number because competition for oviposition sites was reduced. Consequently, wingless foundresses did not adjust their sex ratio when the density of foundresses increased in a fig. Sycoscapter sp. oviposits two-three weeks after pollinator entry. There was no negative correlation present between the number of pollinators and Sycoscapter sp. in the figs, suggesting that the latter might not be a parasitoid. However, in experiments where the numbers of pollinators entering a fig was controlled, Sycoscapter sp. significantly reduced the number of pollinators. It is suggested that Sycoscapter sp.is a parasitoid, or inquiline. It also did not affect the sex ratio of its host