Publication
 

An entomocentric view of the Janzen-Connell hypothesis

We may be able to estimate indirectly the role of insects in ecological processes, but without a good knowledge of the identity and life history of the species involved, our conclusions may be rather subjective. In this essay, we explore the implications of ignoring the identity and traits of insects in the context of the mechanistic drivers of the Janzen-Connell hypothesis (JCH). Research inspired by the JCH represents a significant body of ecological literature and proposes an explanation for the coexistence of tree species in diverse tropical forests. Studies that have assessed the role of specific insect species in causing patterns consistent with the predictions of the JCH tend to be biased towards the Neotropics, open forests, palms or leguminous trees, bruchine beetles and leaf-chewing insects. Scrutiny of other study systems is urgently needed before we can make sweeping conclusions about the generality of Janzen-Connell effects induced specifically by insects. Potential engineers of Janzen-Connell effects may include pre and post-dispersal seed predators, ants removing seeds, vectors of phytopathogens such as sap-sucking insects, and insects able to damage meristems or to completely defoliate seedlings. We conclude that Janzen-Connell effects mediated by insects in tropical rainforests appear to be less likely to be driven by contagion of host-specific species from parent trees to seedlings, but more likely via a combination of escape of seeds from pre-dispersal attack, and attack of seedlings by generalist herbivores in the forest understorey, possibly aggravated by transmission of diseases by insect vectors.

Authors: 
Yves Basset Scott E. Miller Sofia Gripenberg Richard Ctvrtecka Chris Dahl Simon R. Leather Raphael K. Didham
Journal: 
Insect Conservation and Diversity
Year: 
2019
Volume: 
12
Issue: 
1
Pages: 
1-8
DOI: 
10.1111/icad.12337