Introduction Rubiaceae Asclepiadaceae Nepenthaceae Bromeliaceae Orchidaceae Polypodiaceae Ecology and    evolution Cultivation References

Ecology and Evolution      Ant-house plants frequently grow in bright, nutrient poor habitats (Janzen, 1974; Huxley, 1978). This habitat preference is similar to that of carnivorous plants, although the carnivorous plants generally prefer wetter areas and are rarely epiphytes. Both myrmecophily and carnivory seem to be responses to a lack of nutrients. The foraging ants allow the myrmecophytes to gather nutrients from a much wider area than could be reached by their root systems. The apparent distinction between moist carnivorous plant habitats and drier myrmecophyte habitats may indicate that the structures supporting carnivory require more water. Alternatively, it is possible that succulent storage organs possessed by plants in harsher environments are more easily converted into domatia. The domatia of the rubiaceous ant plants probably evolved from such storage organs (Huxley, 1980).      In origin, the association of ants with ant-house plants probably derives from the normal behavior of ants. In the tropics, availability of nesting sites is a limiting factor for ant populations, and epiphytes frequently provide shelter to the ants (Davidson and Epstein, 1989). Primitive ant-house plants might be little different from non-ant inhabited species. For example, Brocchinia reducta does not have specialized structures that support ant nests. As in many bromeliad species, the crevices between leaves in old plants simply form convenient hollows. Storage tubers of Pachycentria glauca are sometimes hollowed out and inhabited by ants (Huxley, 1980). Mutations which make the primitive domatium more attractive to the ants would tend to strengthen the association. A variety of domatia, from simple to complex including intermediate stages, can be seen in living species of Dischidia and Lecanopteris.