Biodiversity of the Domatia Occupants (Ants, Wasps, Bees, and Others) of the Sri Lankan Myrmecophyte Humboldtia laurifolia Vahl (Fabaceae). Smithsonian Contributions to Zoology, Number 603.

摘要

A number of plants throughout the world have entered into facultative or obligate mutualistic relationships with ants, taking advantage of the insect's ability to protect its territority (the plant) by repelling or killing intruders. The plants have evolved numerous methods to ensure an ant's presence, ranging from offering both a domicile and a constant food supply throughout the year to no domicile and temporal sugar-secreting nectaries only. Either situation improves the chances of having ants present on a plant. The ants present may be obligate and restricted to a single specific plant taxon. A single plant species, however, may attract numerous ant taxa, sometimes as many as fifteen. Humboldtia laurifolia Vahl (Fabaceae, Caesalpinioideae) is a common understory tree in the lowland rainforest of Sri Lanka. It is a myrmecophyte, but it also attracts a diversity of other animal life. In this contribution we discuss the variety of organisms interacting with and inhabiting this tree. The internodes (i.e., domatia) of Humboldtia are inflated, hollow cavities that provide nesting sites for ant colonies. In addition to collapse of the central pith against the inner walls of the cavity, a slit-like opening develops at the top of the hollow internode, which allows access to any organism small enough to fit through the opening. The tree also has numerous extrafloral nectaries, which produce sugary secretions where ants and other insects feed. In this mutualistic arrangement, some of the ant species, especially those species nesting in the plant, protect the foliage and flower buds from herbivory. The internodes not occupied by ants furnish nesting sites for solitary or subsocial wasps and bees, as well as shelter for other invertebrates. Some of the latter are predators or parasites of the ants, bees, and wasps nesting in the same plant.