Selective pressure

Definition

Any environmental factor—biotic or abiotic—that differentially affects the reproductive success of individuals within a population, thereby driving natural selection and evolutionary change. Selective pressures may be positive (favoring certain traits), negative (selecting against traits), or balancing (maintaining polymorphism). The intensity and direction of pressure determine which phenotypes increase in frequency across generations.

Etymology

Example

Insecticide resistance in Colorado potato beetle (Leptinotarsa decemlineata) arises when chemical application creates intense selective pressure: beetles with mutations conferring detoxification enzymes survive and reproduce, rapidly shifting population genetics within a few generations.

Synonyms

• selection pressure
• evolutionary pressure

Related Terms

• Natural selection
• Fitness
• Adaptation
• directional selection
• stabilizing selection
• disruptive selection
• genetic drift
• phenotypic plasticity
• resistance evolution

Usage Notes

Often used with modifiers indicating direction (positive/negative/balancing) or source (predation pressure, thermal pressure, desiccation pressure). Distinguish from genetic drift: drift is random change, whereas selective pressure is non-random and fitness-linked. In applied entomology, understanding selective pressure is critical for resistance management strategies such as insecticide rotation and refuge planting.