ANT DISPERSAL OF CROTON PRISCUS (EUPHORBIACEAE) SEEDS IN A TROPICAL SEMIDECIDUOUS FOREST IN SOUTHEASTERN BRAZIL

Seed dispersal of C. priscus was studied in a semideciduous forest in S.E. Brazil. C. priscus is a pioneer tree, with abundant capsules cont aining three elaiosome-bearing seeds. The seeds are explosively disper sed and the mean ballistic dispersal distance for two trees were 3.2 a nd 3.4 m. The explosive ejection of seeds is followed by ant exploitat ion. Eleven ant species were attracted to the elaiosomes of the seeds, bur only two species regularly removed seeds. On average, Atta sexden s and Pheidole sp. 1 move seeds 2.5 and 1.0 m, respectively. The ants usually deposit the seeds in the nest. The seed removal rate was 88 pe rcent: (N = 100) over the first 24 hr of exposure. Our results indicat e that elaiosome removal by ants probably does not improve germination rates in C. priscus. Seeds without elaiosomes and seedlings of C. pri scus were frequent on refuse piles of ant nest in the study area, sugg esting that transport of the seeds by Attini and Pheidolini may provid e beneficial effects in the Croton system.