Observations on ant-plant interactions in Pachycentria and other genera of the Dissochaeteae (Melastomataceae) in Sabah and Sarawak

In Sabah and Sarawak (Malaysia) ant-plant interactions of Dissochaeteae were studied in the field. Whereas some species of Dissochaeteae show only loose and fortuitous interactions with ants as the result of the provision of pearl bodies and nesting places which are used by ants facultatively, Pachycentria constricta and P. glauca show a complex relationship with ants mediated by other ant plants. Both species provide pearl bodies and potential nesting space or shelter for ants in dried out and hollow root swellings. The main characteristic which differentiates them from all other Melastomataceae interacting with ants are their particular seeds which are attractive to ants and carried into their nests. As a result Pachycentria constricta grows in ant gardens, e.g., together with Hoya, and P. glauca is frequently found growing on Hydnophytum and Dischidia. Both species might increase the fitness of the community in which they live by the provision of food in form of pearl bodies and by water storage in their root swellings. In return, Pachycentria constricta and P. glauca are planted in a favourable nutrient-rich environment and perhaps are protected by the ants.