West African Montane Forest Diversity: Testing the Janzen-Connell Model for Species Diversity

A major question in ecology is: Why are tropical forests so species diverse? A leading hypothesis is the Janzen-Connell model, which assumes that the activities of host specific seed/ seedling predators open up space surrounding parent trees and allow for the establishment of non-conspecifics. This model has been tested over 70 times since 1970 but results have been highly variable. Biologists hold divergent views on whether the model can explain the maintenance of tree species diversity. Here I test the Janzen-Connell hypothesis for the first time in a montane forest in Nigeria, West Africa. Specifically I tested whether or not a) leaf herbivory decreases and b) seedling survival increases with distance from parent / conspecific adult trees. These two components were tested separately on naturally occurring and experimentally planted seedlings. I also tested whether or not conspecific adult trees showed clumped distributions by testing if conspecific nearest neighbours were observed more often than would be expected by chance alone.Although results were variable this work aims to illustrate that many factors exist which cause variation in Janzen-Connell test results.