Population Biology of Tropical Rain Forest Trees

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The effects of deforestation on the extinction rates of plant species in tropical rain forests are well documented. Less is known about the impact of deforestation on the loss of genetic variation within tree species because there is not enough information about the amount and patterns of spatial distribution of genetic variation in natural populations. Genetic variation is considered to be important in the long term survival of populations. Thus, information about the amount and patterns of genetic variation within and among populations is central to the design of appropriate measures to conserve tropical tree populations. Equally important is to understand the genetic factors, such as mating systems and the level of gene exchange among populations, which greatly influence the distribution of genetic variation. Many tree species in tropical rain forests have low population density. Small populations may lose genetic variation, and may also be subject to inbreeding depression (deleterious effects in reproductive output due to mating among close relatives). Thus, it is paricularly important to study factors regulating genetic variation in species that typically occur in low densities. The objectives of this research are to 1. analyze the amount and patterns of genetic variation, 2. estimate effective population size, 3. measure the rate of outcrossing (or inbreeding), 4. determine the level of gene exchange among populations, and 5. examine the effects of density on the level of inbreeding and reproductive output in natural populations of tropical lowland rain forest trees. The field work will be conducted at the La Selva Biological Field Station of the Organization for Tropical Studies in Costa Rica, and the laboratory work at the University of Massachusetts at Boston.