Summary 1We studied the dispersal system of the tree Clusia criuva (Clusiaceae) in a tropical rain forest in south-east Brazil. An observational/experimental approach was adopted to estimate the probability of transitions between consecutive stages in the recruitment process (i.e. fruit production and removal by birds, ant-seed interactions on the forest floor, seed germination, and establishment and early survival of seedlings). 2 Clusia trees produce hundreds of capsules with small lipid-rich arillate seeds. Crop size ranges from 393 to 3709 capsules per tree. Birds (14 species) eat 83% of the diaspores on the tree, while the remaining 17% fall to the ground and are removed by ants (16 species). 3 Ants remove 89% of the fallen diaspores and 98% of the seeds found in bird faeces. Ponerine ants ( Odontomachus , Pachycondyla ) carry the diaspores to their nests, while small myrmicines ( Pheidole , Crematogaster ) remove the aril where found. Aril removal by ants and removal of seeds from bird defecations increase germination success in C . criuva . 4 Seedlings are more frequent close to ponerine nests than in control areas without such nests. Early seedling survival (1 year) in nests of Pachycondyla striata is greater than in control areas. Soil samples from nests of P . striata also had higher concentrations of total nitrogen and phosphorus than random soil samples. 5 This is the first study to demonstrate the combined effects of ants on the distribution and survival of seedlings of a primarily vertebrate-dispersed plant in a tropical forest.

Fleshy diaspores (fruits, seeds) comprise a large portion of the litter on the floor of tropical forests, and interactions involving litter-foraging ants and diaspores are common in these areas. In this study, the interactions between ants and non-myrmecochorous diaspores (i.e. not adapted to dispersal by ants) were surveyed along a 1.4-km transect in a restinga forest (sandy soil) on the coast of south-eastern Brazil. During 2 y of monthly samplings, 562 interactions involving 48 ant species and 44 species of diaspore (0.02–11.10 g) were recorded. Ant–diaspore associations involved a considerable part of the ground-dwelling ant community. Large ponerine ants individually removed the diaspores up to 13 m, whereas small ants (myrmicines) normally recruited workers and consumed the diaspore on the spot. Ant-derived benefits to diaspores of non-myrmecochorous plants included secondary dispersal (small to medium-sized diaspores), and increased germination success after seed cleaning by ants. Large ponerine ants such as Odontomachus chelifer and Pachycondyla striata were the main seed vectors. Seedlings of three species were associated with nests of O. chelifer. The results indicate that ants play an important role in fruit/seed biology in the restinga forest.

This study examines the dispersal system of Guapira opposita in a tropical sandy rainforest in southeast Brazil. Guapira trees produce small fruits with a high protein content (28.4%) and low lipid content (0.3%), and the plant is primarily dispersed by birds. Mature fruits of G. opposita can fall spontaneously with the pulp intact, or be dropped by birds with bits of pulp attached. In either case, ground-dwelling ants rapidly remove the fruits to their nest (93% after 12 h). The ponerine ants Odontomachus chelifer and Pachycondyla striata are the main seed vectors among the ants, and together account for 56% (20 of 36) of the ant-fruit interactions recorded on the forest floor. Individual workers of O. chelifer and P. striata transport single fruits to their nests. Bits of pulp are fed to larvae and worker nestmates, and intact seeds are discarded outside the nest. Germination success in Guapira is higher for cleaned seeds (pulp removed) than for seeds coated by pulp. Guapira seedlings and juveniles are more frequent close to Odontomachus nests than at sites without such nests. Soil samples from Odontomachus nests had greater penetrability, and higher concentrations of P, K, and Ca than random soil samples. Field experiments suggest that the association between G. opposita seedlings and O. chelifer nests can potentially render the plant some protection against herbivores. Results indicate that fruit displacement by ponerine ants play an important role in the biology of G. opposita seeds and seedlings in the sandy forest, and illustrate the complex nature of the dispersal ecology of tropical tree species.

The reproductive biology of Manettia luteo-rubra was studied in the coastal montane Atlantic rain forest of southeastern Brazil. This Rubiaceae is a perennial vine that flowers all the year round, but has a flowering peak during the dry season. It presents reciprocal herkogamy, thus the plants are morphologically distylous. The morphs occur in a 1 : 1 ratio, and pollen diameter and corolla length vary between short and long-styled flowers. Manettia luteo-rubra displays typical heterostylous self-incompatibility and sets almost no fruits from self-or intramorph pollinations. The flowers are tubular, red with yellow lobes, and odourless. Anthesis is asynchronous, and the flowers last about four days. Concentration of sugars in nectar is similar in both morphs, ca. 24 YO, this concentration being typical for hummingbird flowers. Three species ofhummingbirds are the major pollinators of the flowers ofM. luteo-rubra at the study site: the hermits Phaethornis eurynome and P. squalidus, and the trochiline Thalurania glaucopis. Three species of Heliconius butterflies act as minor pollinators. Both morphs of M. luteo-rubra exhibit natural fruit-set of about 80 YO, this reproductive output being maintained throughout the year by the pollinators' constancy to the flowers. Kev wordsHeterostyly, breeding system, floral biology, hummingbird pollination, butterfly pollination.

This paper provides an overview of recent studies describing: (1) ant and plant species involved in the ant-diaspore interactions; (2) attributes of ants and diaspores that mediate the interaction; and (3) possible consequences of the interaction for plants. A study examined how these interactions vary spatially by comparing the patterns of selected ant-diaspore interactions occurring at two main study areas in the Brazilian Atlantic Forest (Sao Paulo): lowland forest and sandy plain forest (locally called 'restinga'). It is demonstrated that in the study area ground-dwelling ants interact frequently with fallen vertebrate-dispersed diaspores and that this may render recruitment benefits for some plant species. Possible causes underlying such patterns are examined and discussed, and avenues of future research are suggested.