Data from: Incorporating the disease triangle framework for testing the effect of soil-borne pathogens on tree species diversity

1. The enemies-induced Janzen-Connell (JC) effect, a classic model
invoking conspecific negative density dependence (CNDD) and distance
dependence, is a primary biodiversity maintenance hypothesis. Yet,
conflicting evidence for the JC effect leads to disagreement about its
role in maintaining forest diversity. 2. We focus this review on
soil-borne pathogens, which are the primary agent inducing the JC effect
in many forest ecosystems. Although the test of the pathogen-induced JC
effect in ecology critically rests on the seedling mortality caused by
soil pathogens, what has not been explicitly explored in the early
literature but has increasingly received attention is the long-recognized
fact that the environment can alter virulence of pathogens and host
susceptibility (and thus pathogen-host interactions), as predicted by the
classic disease triangle framework enlightened by pathology research in
agricultural systems. 3. Here, following the disease triangle framework we
review evidence on how the pathogen-induced JC effect may be contingent on
context (e.g., environmental conditions, pathogen inoculum load, and
genetic divergence in host and pathogen populations). The reviewed
evidence reveals and clarifies the conditions where pathogens may or may
not cause disease to hosts, thus contributing to reconciling the
inconsistent results about the pathogen-induced JC effect in the
literature. The context-dependence of the disease triangle predicts that
the pathogen-induced JC effect would change under global change. 4.
Gaining insights from evidence that the pathogen-induced JC effect is
context-dependent, we suggest that future tests on the JC hypothesis be
conducted under the framework of disease triangle, and we stress the
necessity by controlling the effect of context factors on plant-pathogen
interactions when testing for the JC effect. We conclude the review by
proposing three lines of future research for testing the importance of the
JC effect in maintaining global forest tree species diversity, with a
particular emphasis on testing the effect of global warming on the
strength of pathogen-host interactions for better predicting changes of
forest biodiversity under climate change.