Ficus Rubiginosa - Ecology

Ecology

As with all figs, the fruit is actually an inverted inflorescence known as a syconium, with tiny flowers arising from the inner surface. Ficus rubiginosa is monoecious — both male and female flowers are found on the same plant, and in fact in the same fruit although they mature at different times. Ficus rubiginosa is pollinated by a symbiotic relationship with a fig wasp species (Pleistodontes imperialis). The fertilised female wasp enters the receptive 'fig' (the syconium) through a tiny hole at the crown (the ostiole). She crawls around the inflorescenced interior of the fig, pollinating some of the female flowers. She then lays her eggs inside some of the flowers and dies. After several weeks' development in their galls, the male wasps emerge before the females. They chew holes in the galls containing females and fertilise them through the hole they have just chewed. Males return later to mated females, and enlarge the mating holes to enable the females to emerge. Some males then chew their way through the syconium wall, which allows the females to disperse after collecting pollen from the now fully developed male flowers. Females then have a short time (< 48 hours) to find a tree with receptive syconia to successfully reproduce and disperse pollen.

A field study in Brisbane found that a F. rubiginosa trees often bore both male and female syconia at the same time, which could be beneficial for reproduction in isolated populations. The same study found that male phase syconia development persisted through the winter, showing that its wasp pollinator tolerated cooler weather than those of more tropical fig species. F. rubiginosa itself can endure cooler climates than other fig species.

Pleistodontes imperialis traversed the waters between Australia and New Zealand some time between 1960 and 1972, and seedlings of the previously infertile trees of F. rubiginosa began appearing in brick and stone walls, and on other trees, particularly in parks and gardens around Auckland. They have been recorded as far south as Napier.

The fruit is consumed by many bird species including the Rose-crowned Fruit-dove (Ptilinopus regina), Wompoo Fruit-dove (P. magnificus), Wonga Pigeon (Leucosarcia melanoleuca), Topknot Pigeon (Lopholaimus antarcticus), Australasian Figbird (Sphecotheres vieilloti), Green Catbird (Ailuroedus crassirostris), Regent Bowerbird (Sericulus chrysocephalus), Satin Bowerbird (Ptilonorhynchus violaceus), Pied Currawong (Strepera graculina), and Pacific Koel (Eudynamys orientalis). The Spectacled Flying-fox (Pteropus conspicillatus) eats the fruit.

The thrips species Gynaikothrips australis feeds on the underside of new leaves of F. rubiginosa, as well as F. obliqua and F. macrophylla. As plant cells die, nearby cells are induced into forming meristem tissue and a gall results, and the leaves become distorted and curl over. The thrips begin feeding when the tree has flushes of new growth, and the life cycle is around six weeks. At other times, thrips reside on old leaves without feeding. The species pupates sheltered in the bark. The thrips remain in the galls at night and wander about in the daytime and return in the evening, possibly to different galls about the tree.