The Janzen-Connell hypothesis (JC) is one potential mechanism to explain the maintenance of high alpha diversity of tree species in tropical forests, operating through differential pressure by natural enemies. Constraints on the populations of common species could arise from a greater diversity of natural enemies. If the mechanism of negative density-dependence (conspecific effect) is at the center of many studies, testing the JC from an aboveground natural enemy diversity point of view has never been done. The objectives of this work were to test the new interpretation of the JC, assess the variability of the negative density-dependence (a more traditional way to test the JC) over time, and to offer a new conceptual model of seedlings community abundance. By assessing damage patterns on leaves, as a proxy for natural enemy species, I was able to prove that seedlings of common tropical trees host a higher diversity of aboveground natural enemies than seedlings of rare tropical trees. I also found that this resulted in a disadvantage in common species due to higher mortality risk due to aboveground foliar damage. However, from a negative-dependence perspective, common species are more often advantaged compared to rare species. These findings bring support for our interpretation of the JC. I then developed the conceptual model to reunify this interpretation and the variability of NDD. This theoretical model predicts that seedling abundance will oscillate between being rarer and more common over ecological time. The results offer a different step in understanding high tree species diversity in the tropics.
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