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In Amazonian rain forest trees of Vochysia vismiaefolia (Vochysiaceae), ants were found to induce twig structures that resembled classical ant domatia. This phenomenon is novel for ant-plants, which commonly develop domatia without the activity of ants. Eight species of ants were recorded inside the domatia of six individual trees, but domatia were most numerous and characteristic when induced and inhabited by an undescribed species of Pseudomyrmex on two trees. To investigate the mechanism of domatium growth, we drilled holes into young twigs: the expansion of the twig diameter surrounding the holes was significantly accelerated, comparable to domatia formation. Domatia induction is discussed as a putative step in the evolution of ant-plants.

The taxonomic distribution and abundance of woody plants with extrafloral nectaries (EFNs) are reported for different areas of cerrado vegetation (subtropical savanna) in the state of Sao Paulo, southeast Brazil. Thirty-four plant species belonging to 15 families were found to have EFNs. The Mimosaceae (6 species) and Bignoniaceae and Vochysiaceae (4 species each) were the families most frequently bearing EFNs. Glands associated with vegetative parts (leaves, stem) were more common (91.2%) than those found near the bud or flower (20.6%). The percentage of EFN-bearing species within the woody floras of 5 cerrado areas in Sao Paulo ranged from 15.5 to 20.2. The abundance of plants with EFNs in these areas varied from 7.6 to 20.3 percent. These results are compared with data obtained from other similar studies undertaken in temperate and tropical habitats.