Predation starts small: rethinking an ecological concept from microbes to macrobes

Predation is a central concept in ecology, structuring food webs, population dynamics, and evolutionary processes. Despite its importance, ecologists have long disagreed on how predation should be defined. Many influential definitions implicitly rely on adaptationist assumptions, treating predation as killing for feeding by organisms evolved for prey capture. This paper argues that such definitions generate conceptual and empirical difficulties, especially when predation is examined beyond familiar macroscopic systems. Microbial interactions frequently involve killing followed by consumption of victim-derived nutrients, yet these interactions are often excluded from predation due to the absence of stable predator–prey roles or clear evidence of adaptive specialization. I propose a process-based definition of predation as the killing and consumption of one organism by another, independent of evolutionary history. This account aligns predation with causal-role approaches to ecological function, preserves empirical tractability, and clarifies boundaries between predation, competition, and scavenging. By integrating microbial and macrobial systems within a single conceptual framework, the paper shows how rethinking predation improves ecological explanation across scales.