Distance-responsive predation is not necessary for the Janzen-Connell hypothesis

Area of Science:

• Ecology
• Tropical Biology
• Forest Dynamics

Background:

• The Janzen-Connell hypothesis proposes that specialist predators maintain tropical tree diversity by reducing seedling survival near adult trees.
• Empirical research has focused on predator distance-responsiveness, but its impact on diversity maintenance remains under-examined.

Purpose of the Study:

• To analytically investigate the role of distance-responsive versus non-distance-responsive specialist predators in maintaining tropical tree diversity.
• To assess the interaction between predator responsiveness and other ecological mechanisms like habitat partitioning on species coexistence.

Main Methods:

• Utilized a site-occupancy model to analyze predator-prey dynamics and their effect on tree recruitment.
• Developed analytical solutions to evaluate how predator responsiveness influences species coexistence.

Main Results:

• Distance-responsive predators are less effective at maintaining tree diversity compared to non-distance-responsive specialist predators.
• High seed predation rates can persist even with low predator density if seeds cannot disperse away from distance-responsive predators.
• Habitat partitioning can lead to higher recruitment near conspecific adults, independent of predator effects on coexistence.

Conclusions:

• The effectiveness of specialist predators in maintaining tropical tree diversity is contingent on their responsiveness to host density.
• Distance-responsiveness may not enhance, and could potentially reduce, a predator's ability to maintain diversity.
• Specialist predators and habitat partitioning act additively, rather than interactively, in promoting species coexistence in tropical forests.