Can we predict indirect interactions from quantitative food webs?--an experimental approach

Area of Science:

• Ecology
• Entomology
• Food web dynamics

Background:

• Apparent competition, driven by shared enemies, is often inferred from quantitative food webs.
• Theoretical models predict diverse outcomes, including positive interactions, challenging negative assumptions.

Purpose of the Study:

• To experimentally link food web patterns to realized population dynamics of leaf miners.
• To investigate indirect effects between herbivorous insect species sharing parasitoids.
• To test if experimental findings align with natural population dynamics.

Main Methods:

• Constructed a quantitative food web for three dominant oak leaf miner species.
• Measured short- and long-term indirect effects by manipulating leaf miner densities.
• Compared experimental results with natural population dynamics on unmanipulated trees.

Main Results:

• Leaf miner species sharing more parasitoids exhibited positive interactions over years, not negative.
• Intraspecific density-dependent parasitism was observed in Tischeria ekebladella.
• No short-term indirect interactions were detected between leaf miner species within a single generation.

Conclusions:

• Herbivores with overlapping parasitoid communities can display independent population dynamics or apparent mutualism.
• Demonstrates versatile indirect interactions in ecological communities.
• Highlights the necessity of experimental validation for food web pattern inferences.