Ant-Seed Interaction in Dry Sclerophyll Forest on North Stradbroke Island, Queensland

Abstract

The rate of removal by ants of diaspores of 15 species, 10 with elaiosomes, was studied in dry sclerophyll forest. Two ants were largely responsible, Rhytidoponeva metallica and Aphaenogaster longiceps. The rapid removal of diaspores by ants greatly depletes in a very short time the readily available seed supply for regeneration, especially if diaspores are taken to an unsuitable germination site.

All plant species but one (Lepidospevma laterale) are placed in established ant dispersal types. A new type, Lepidosperma, is proposed. Eucalyptus seeds lack an appendage and the ant relationship to them is complex. Nevertheless, ants rapidly remove seeds of Eucalyptus when they are offered. Oil in the embryonic cotyledons is probably the food supply.

Nests of R. metallica are mostly built in association with pieces of wood while those of A. longiceps occur in the soil. Rate of removal is influenced by distance from the nest, number of ants, time of day or year, size and shape of diaspores and intensity of 'scent'.

Successful dispersal by ants is related to the food source and the type and depth of nest. Food is obtained from appendaged diaspores without damage to the embryo. Seeds in R. metallica nests are unlikely to germinate. Depth of burial will affect germination. seedling emergence and dormancy breaking. Seeds for regeneration of Eucalyptus are probably available through predator satiation. Ants appear to be successful short-distance dispersal agents for a small proportion of diaspores that remain undamaged and are buried in a suitable germination site.