Gradients in predation risk in a tropical river system

Area of Science:

• Evolutionary Ecology
• Behavioral Ecology
• Community Ecology

Background:

• Predation risk is a key driver of evolutionary change, as seen in Trinidadian guppies.
• Previous studies often simplified predation risk into dichotomous high or low categories.
• Ecologists recognize that predation risk varies significantly across space and time due to community structure.

Purpose of the Study:

• To quantify temporal and spatial variation in predation risk at 16 sites in Trinidad's Northern Range.
• To investigate if predation risk forms a gradient.
• To determine if site rankings by risk change based on predator community definition and if rankings are consistent over time.

Main Methods:

• Longitudinal study of fish assemblages at 16 different sites.
• Quantification of temporal and spatial variation in predation risk.
• Analysis of how predator species composition and abundance currency affect site risk rankings.

Main Results:

• Evidence supports a continuum of predation risk across sites, rather than discrete high/low categories.
• Site rankings along the predation risk gradient are influenced by the definition of the predator community (species and abundance currency).
• Despite variations in definition, site rankings show relative consistency over time for a given categorization.

Conclusions:

• Understanding predation risk requires considering gradients rather than simple dichotomies.
• The definition of predation risk (predator species and abundance currency) significantly impacts ecological and evolutionary interpretations.
• Consistent site rankings over time, for specific definitions, support the utility of gradient-based approaches in evolutionary ecology.