9307878 Hamrick While surveys of genetic diversity in tropical tree species are numerous enough to make some generalizations (high within population diversity, relatively low diversity among populations, much species-to-species variation in genetic diversity) We know very little about the underlying mechanisms that influence the levels and distribution of genetic diversity in tropical trees. The relatively low levels of differentiation seen among tropical tree populations indirectly indicates that gene movement over rather large geographic distances (5-10km) is high, but here are very few studies available that have made quantitative estimates of gene movement. Those estimates that are available are consistent with the levels of differentiation seen among populations. Unfortunately, the species richness of tropical forest and the wide array of pollen and seed dispersal agents available to tropical trees makes generalizations based on a few studies questionable at best. The proposed research will increase the number of species for which estimates of gene flow are available under natural conditions. The comparative nature of this research, while based on a relatively few species will extend our knowledge of gene movement in tropical tree species to several pollination syndromes that have not been studied to date. Upon its completion this research will greatly extend our understanding of gene movement in tropical forest.%%% By studying effective pollen immigration into isolated forest fragments we will extend our evolutionary studies into the realm of applied conservation biology. Any management plan with the goal to preserve forest tree species and their genetic resources will need to know the degree of gene movement among forest fragments and the levels of inbreeding they experience. Also our work will begin to determine the effects of isolation distance on levels of gene flow and how these relationships vary for species with different pollinati on syndromes. Knowledge of the levels of gene movement and the spatial scales at which it occurs may ultimately allow the development of landscape level designs that accommodate agricultural development but at the same time preserve the biological and genetic diversity of tropical tree species.***
