XVI International Botanical Congess

Allozyme loci were used to describe the breeding structure of fragmented populations of Enterolobium cyclocarpum (Fabaceae: Mimosoideae), a dominant tree of the seasonally dry tropical forests of Costa Rica. Several reproductive events were analyzed. Due to the presence of full-sibs withinindividual fruits, the exact multilocus genotype of each pollen parent could be inferred. Comparisons of pollen donor pools made among trees within sites and among years indicated that most trees received pollen from large numbers of pollen parents. Trees within clusters tended to have fewer pollen donors while isolated trees experienced more pollen donors. The similarity of pollen donor pools ranged widely among trees within individual sites and among years for individual trees. Rates of gene flow averaged approximately 60%.