This topic has dominated my research career. In particular, I am interested in understanding how so many tree species coexist in tropical rainforests. One intriguing mechanism is the Janzen-Connell hypothesis, which suggests that fungal pathogens and insect herbivores exert negative density-dependent control of plant populations.

Our work in Malaysia and Belize supports several elements of this hypothesis, confirming that some tropical seedlings do seem to be controlled by negative density dependence and implicated fungal pathogens as likely drivers.

Current work is using a combination of field studies and new spatial statistical approaches to test the predictions of the Janzen-Connell hypothesis in additional sites and species and understand the causes of variation in negative density dependence among species and environments.