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Do Reverse Janzen-Connell Effects Reduce Species Diversity?

Shafia Zahra¹, Vojtech Novotny¹, Tom M Fayle²

¹Biology Centre of the Czech Academy of Sciences, Institute of Entomology, Branisovska 31, 370 05 Ceske Budejovice, Czech Republic; Faculty of Science, University of South Bohemia, Branisovska 31a, 370 05 Ceske Budejovice, Czech Republic.

Trends in Ecology & Evolution

|March 3, 2021

Summary

This summary is machine-generated.

Host-specific natural enemies boost community diversity by limiting common species, known as the Janzen-Connell effect. Conversely, host-specific mutualists can reduce diversity by increasing certain species

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Area of Science:

Ecology
Community Ecology
Biodiversity Studies

Background:

The Janzen-Connell effect describes how natural enemies specific to a host plant limit its abundance, promoting higher community diversity.
This ecological principle explains how specialist predators or pathogens can prevent single species from dominating plant communities.

Purpose of the Study:

To introduce and define the concept of a 'reverse Janzen-Connell effect.'
To highlight emerging evidence suggesting that host-specific mutualists can have an opposite impact on community diversity compared to natural enemies.

Main Methods:

Literature review and synthesis of existing ecological studies.
Conceptual framework development for the 'reverse Janzen-Connell effect.'

Main Results:

Accumulating evidence indicates that mutualistic interactions can increase the abundance of specific host species.
This increase in dominant species, driven by mutualists, leads to a reduction in overall community diversity.

Conclusions:

Host-specific mutualists can decrease community diversity, acting as a 'reverse Janzen-Connell effect.'
This contrasts with the diversity-enhancing role of host-specific natural enemies.
Further research is needed to fully understand the implications of mutualism on community structure and diversity.