Direct effects influence larval salamander size and density more than indirect effects

Area of Science:

• Ecology
• Population Dynamics
• Community Ecology

Background:

• Direct and indirect ecological effects shape populations and communities.
• In situ evaluation of these effects is less common than experimental approaches.

Purpose of the Study:

• To examine direct and indirect effects on larval salamander density and body size.
• To quantify the relative importance of these pathways in natural pond ecosystems.

Main Methods:

• Surveyed over 150 ponds in Missouri, USA (2012-2014).
• Measured larval density, body size, co-occurring species density, and habitat features.
• Utilized structural equation modeling to analyze direct and indirect pathways.

Main Results:

• Both larval density and body size were influenced by direct and indirect effects.
• Direct effects were generally stronger than indirect effects.
• Habitat and density variables sometimes canceled each other's impacts, weakening overall effects.

Conclusions:

• Direct effects are as important, or more so, than indirect effects on larval salamanders.
• Individual relationships can sum to produce negligible net population patterns.
• Observational studies are crucial for understanding effect magnitudes in natural communities.