The Escola Superior de Agricultura “Luiz de Queiroz” (ESALQ) of the University of Sao Paulo, Piracicaba, Brazil, has over the past years carried out studies on genetic structure of populations of some native Brazilian tropical tree species as a basis for their sustainable use and conservation in situ. The studies have been conducted with support from FAO's Forestry Department. Recent research within this framework of collaboration has included the following:
SPATIAL DISTRIBUTION OF TROPICAL TREE SPECIES
The spatial distribution patterns of two species, Euterpe edulis and Esenbeckia leiocarpa, were studied in the Atlantic Tropical Forest of Brazil. E. edulis is evenly distributed throughout the forest, whereas E. leiocarpa was found to occur in pronounced clusters, with obvious implications for the design and management of conservation areas (see below). Additional research is planned for the future, especially on the distribution patterns and genetic structure of species occurring in low densities in the forest (less than one individual per hectare), as there are grave problems to adequately sample such species and the variation they contain, when planning in situ conservation of their genetic resources.
REPRODUCTIVE BIOLOGY OF TROPICAL TREE SPECIES
Studies were carried out on (1) species diversity in soil seed banks and (2) predation of seeds of Chorisia speciosa. The latter study showed a clear negative correlation between the numbers of predators and the distance from the mother tree. A hypothesis links the distribution of some species to the association between tree and predator.
DETERMINATION OF GENETIC VARIATION OF TROPICAL TREE SPECIES THROUGH PROGENY TESTING
Two species were tested, a pioneer: Cecropia sp.; and a climax species: Esenbeckia leiocarpa. The progeny was tested under ecological conditions simulating a natural ecosystem. Results for E. leiocarpa showed a high overall variability, and more variation between clusters of individuals than within them. The clustered, natural occurrence of the species and the likely, infrequent cross-pollination between clusters, could at least partly explain such distribution of extant variation in this species.
STUDY OF GENETIC VARIATION IN NATURAL POPULATIONS THROUGH THE USE OF ISOZYMES
The genetic variation in natural populations of Hevea brasiliensis; and the variation within and between two populations of Astronium urundeuva, were studied using electrophoresis. The technique seemed to be an useful tool to determine variation in allozymes. Additional and complementary studies are needed to relate variation in allozymes to morphological variation of the species studied.
For further information please contact Dr. P.Y. Kageyama, ESALQ, Universidade de Sao Faulo, Caixa Postal 9, Piracicaba S.P., CEP 13 400, Brazil.
