Introduction Rubiaceae Asclepiadaceae Nepenthaceae Bromeliaceae Orchidaceae Polypodiaceae Ecology and    evolution Cultivation References myrmecophytic tillandsias Tillandsia disticha Brocchinia acuminata

Bromeliaceae      A number of bromeliad species root into arboreal ant nests and are a component of complex "ant gardens" which derive nutritional benefit from the ants and help to stabilize the nest (Davidson and Epstein, 1989). Species from three genera are ant-house plants. Myrmecophytic tillandsias house ants in their leaf axils, which form a hollow bulb-like structure. Unlike many bromeliads whose leaves channel water towards a central reservoir, myrmecophytic tillandsias have pointed leaf tips that shed rain and keep the ant colony dry. Trichomes on the leaves which typically absorb moisture and windborn minerals also probably serve to absorb minerals from the ants' waste (Huxley, 1980). The myrmecophytic species include Tillandsia bulbosa, T. butzii, T. caput-medusae, and T. pseudo-baileyi. The genus Aechmea includes numerous ant-garden species and one possible ant-house plant, Aechmea brevicollis. As in the myrmecophytic Tillandsias, leaves of Aechmea brevicollis channel water away from the center of the plant.      The genus Brocchinia contains one ant-house species and one species that may combine carnivory with myrmecophily. Brocchinia acuminata is an unambiguous ant-house plant. B. acuminata shares with the myrmecophytic tillandsias a general structure that includes a hollow bulb-like base constricted at the top to keep out rain. Givnish et al. (1997) report that 50% of B. acuminata plants examined in Venezuela were inhabited by ants. Large foliar scales at the base of the leaves are capable of absorbing amino acids, and roots often penetrate the hollow spaces, suggesting that B. acuminata obtains nutrients from its ant inhabitants (Givnish et al., 1997).      Like the Asian Nepenthes bicalcarata, Brocchinia reducta may be both an ant-house plant and a carrnivore (or a sub-carnivore since it traps insects but does not produce digestive enzymes). B. reducta grows alongside the carnivorous pitcher plant Heliamphora nutans in the highlands of Venezuela. Both H. nutans and B. reducta trap ants, and young B. reducta plants contain approximately the same number of trapped ants as the unambiguously carnivorous Heliamphora (Gonzalez et al., 1991). The tightly furled leaf-rosette of B. reducta forms a pitcher that fills with rain water. Insects which drown are broken down by bacterial decomposition, and the released nutrients are absorbed by trichomes on the leaf (Givnish et al., 1984, 1997). Like Nepenthes, Heliamphora uses nectar to attract the ants. Young Brocchinia reducta plants produce a nectar-like fragrance which may also serve as an attractant, but they do not reward the ants with any real nectar (Gonzalez et al., 1991).      Although young specimens of Brocchinia reducta are sub-carnivorous, larger specimens may function as ant-fed ant-house plants. Gonzalez et al. (1991) report that colonies of the same ant species that is preyed upon by younger plants build their nests between the leaves of older plants. The ants use the central tank as a debris dump. A species of spider that often builds webs in Brocchinia reducta rosettes also drops the remains of its meals into the tank.      A third highland species, Brocchinia hechtioides also seems to be sub-carnivorous (Givnish et al., 1997), but there are no reports that it houses ant colonies.