EVIDENCE FOR DISPERSAL OF FIG SEEDS BY THE FRUIT-EATING CHARACID FISHBRYCON GUATEMALENSIS REGAN IN A COSTA-RICAN TROPICAL RAIN-FOREST

Studies were conducted at the La Selva Biological Station in the Atlan tic lowlands of Costa Rica and in a greenhouse in California to assess the potential role of a Neotropical fish in dispersing the seeds of a rain forest tree. Feeding experiments showed that the seeds of Ficus glabrata H. B. K., a major, canopy-forming riparian tree, require appr oximately 18-36 h to pass through the digestive tract of Brycon guatem alensis Regan, an abundant riverine fish whose adult diet consists lar gely of leaves and fruits of this fig tree. The seeds were still viabl e after passing through the fish's gut but germinated somewhat more sl owly than seeds that had been left in the fig exposed to air or floate d in water. Stem elongation of seedlings from seeds that had passed th rough the fish's gut was faster than that of seeds in the other two tr eatments. Placement of seeds upstream may be more important than enhan ced germination for plants such as Ficus that produce large numbers of seeds. Radio telemetry showed that five of six tagged fish had moved distances of 0.1-1 km upstream; seven other fish with transmitters, in cluding three large males, were not relocated and may have moved into tributary streams for spawning or feeding. These findings suggest that . Brycon can disperse large numbers of Ficus seeds and help maintain t he upstream populations of the tree.