Decreasing Predator Density and Activity Explains Declining Predation of Insect Prey along Elevational Gradients

Area of Science:

• Ecology
• Macroecology
• Predator-prey dynamics

Background:

• Predation is a key ecological force, but its intensity typically decreases with increasing elevation and latitude.
• The underlying mechanisms driving this macroecological pattern are not well understood.

Purpose of the Study:

• To investigate the mechanisms behind the decline in predation intensity along elevation gradients.
• To identify the specific predators and factors contributing to this pattern in the equatorial Andes.

Main Methods:

• Conducted visual sampling of predators and used live insect baits along 4,000-meter elevation transects.
• Quantified predation events and identified predator types at different altitudes.

Main Results:

• Ants accounted for approximately 80% of predation events at lower elevations.
• Predation decline with elevation was primarily driven by a decrease in ant abundance and their relative importance.
• Both predator density and individual predator activity (predation rate) decreased significantly with increasing elevation.

Conclusions:

• The study identifies decreased predator density and activity as key mechanisms explaining reduced predation at higher elevations.
• These changes are potentially linked to temperature-influenced primary productivity and metabolic rates.
• Findings have implications for understanding macroecological patterns in predator-prey interactions, especially for ectotherms.