Intrinsic rate of increase

Definition

The per capita rate of population growth under ideal conditions, with no resource limitation, predation, or other density-dependent constraints; symbolized r or r_m. It represents the maximum reproductive potential of a population, derived from age-specific survival and fecundity schedules. In insect ecology, r serves as a benchmark for comparing life-history strategies and predicting population response to environmental change.

Etymology

Example

The aphid Myzus persicae achieves an intrinsic rate of increase of approximately 0.30 per day at 20°C, enabling exponential population growth that can overwhelm host plants within a single growing season; this value declines sharply above 28°C as thermal stress reduces fecundity.

Synonyms

• Malthusian parameter
• Biotic potential
• r_max

Related Terms

• Carrying capacity
• finite rate of increase
• net reproductive rate
• generation time
• Life table
• density-dependent regulation
• population growth curve

Usage Notes

Distinguished from the realized rate of increase, which incorporates actual environmental constraints. Often denoted r_m (intrinsic, with subscript m for Malthus) in demography to emphasize ideal conditions. Compare with R_0 (net reproductive rate), which measures lifetime fecundity per individual rather than per-unit-time growth. In biological control, pest species with high r values require more frequent natural enemy releases to achieve suppression.