Facilitation costs and benefits function simultaneously on stress gradients for animals

Area of Science:

• Ecology
• Environmental Science
• Animal Behavior

Background:

• Understanding species interactions along environmental stress gradients is key for ecological predictions.
• The stress-gradient hypothesis (SGH) is well-established for plants, but mechanisms in mobile animals are less explored.
• Existing frameworks often overlook the dual role of costs and benefits in these interactions.

Purpose of the Study:

• To propose and experimentally test a conceptual framework for changes in facilitation costs and benefits along stress gradients in animals.
• To investigate the fitness outcomes of benefactor-beneficiary interactions under varying resource quality.
• To determine if the stress-gradient hypothesis applies to mobile animal species.

Main Methods:

• Developed a conceptual model of facilitation costs and benefits across stress gradients.
• Experimentally tested the model using three arthropod models: aquatic detritivores, potato moths, and rainforest carrion beetles.
• Measured fitness outcomes of benefactor-beneficiary interactions under different resource quality levels.

Main Results:

• Observed a shift towards more positive interactions (facilitation) as environmental stress increased, supporting the SGH for mobile animals.
• Most benefactors experienced no significant cost of facilitation.
• Increased potato moth beneficiary growth under high resource stress led to costs for their benefactors.

Conclusions:

• The study provides the first experimental evidence of simultaneous costs and benefits in animal interactions along stress gradients.
• The findings support the applicability of the stress-gradient hypothesis to mobile animal communities.
• The proposed framework can guide future research on species interactions in a changing world.