Many tropical plants produce food rewards (e.g., extrafloral nectaries, unicellular pearl glands and multicellular food bodies) that attract and maintain predaceous ants on their foliage. Ants have been shown to spend more time on plants with these rewards, to interfere with potential herbivores and to significantly reduce herbivore damage. Ant-plants, or myrmecophytes, are more specialized in their association with ants because in addition to providing food rewards they possess domatia within which obligate ant species reside. The majority of the approximately 80 species of the Neotropical plant genus Cecropia are myrmecophytes and have hollow stems with thin, unvascularized regions (prostomata) through which ants gain access inside. They produce Müllerian bodies containing protein, lipids and glycogen, and obligate ant inhabitants (e.g., certain Azteca species) are believed to forage exclusively upon them. Cecropia-obligate Azteca ants have been found to be effective at reducing vine growth, in discouraging particular herbivores from feeding and in reducing overall levels of herbivory. However, there are herbivores that can feed on Cecropia in the presence of Azteca because they have chemical and/or morphological defenses, or because they are concealed in their feeding habit. If Azteca ants are successful at detecting and removing some herbivores, then they may be capable of interfering with parasitoids of herbivores they are not able to remove. In Costa Rica I have observed parasitism levels of leaf miners to be lower on Cecropia trees occupied by more active colonies of Azteca. This result is novel, particularly for ant-plant systems, because while ants are known to decrease parasitism levels of actively tended honeydew-producing Homoptera and lycaenoid butterfly larvae and pupae, they have not been shown to provide protection (i.e., enemy free space) for herbivores that do not confer a benefit.
Species 2: Hymenoptera Formicidae Azteca ovaticeps
Keywords: enemy free space, parasitism levels
The ESA 2001 Annual Meeting - 2001: An Entomological Odyssey of ESA