Antagonistic selection from predators and pathogens alters food-web structure.

Area of Science:

• Ecology
• Evolutionary Biology
• Environmental Science

Background:

• Predator-prey interactions are fundamental to food web dynamics.
• The impact of multiple, opposing selective pressures on complex food webs remains poorly understood.

Purpose of the Study:

• To investigate how antagonistic selection from predators and pathogens on prey body size influences food web functioning.
• To determine the relative importance of different selective forces in driving ecological change.

Main Methods:

• Field study in Windermere, UK, examining predator-prey dynamics between pike (Esox lucius) and perch (Perca fluviatilis).
• Analysis of how selection pressures from pike and a perch-specific pathogen affected perch body size and growth rates over time.
• Correlation of selective pressure shifts with changes in food web structure and population dynamics.

Main Results:

• Pike selected against smaller perch, while a pathogen selected against larger perch.
• Shifts in the dominant selective pressure (predator vs. pathogen) led to rapid changes in perch body size and growth.
• These trait changes had cascading effects on trophic interactions, predator-prey dynamics, and overall food web structure.

Conclusions:

• The relative strength and direction of multiple selective pressures are critical for understanding community functioning.
• Synergistic, rather than competitive, interactions between predators and pathogens can drive rapid prey trait evolution and alter food webs.
• This study highlights the need to consider complex selective landscapes in ecological research.