Euler–Lotka growth and age structure
In a fixed density-independent age model, the growth factor λ satisfies Σ_{x≥1}λ^(−x)l_xm_x=1.
Key knowledge
In a fixed density-independent age model, the growth factor λ satisfies Σ_{x≥1}λ^(−x)l_xm_x=1. For continuous age a, survival l(a) and daughter-production rate b(a), the corresponding exponential rate r satisfies ∫₀∞e^(−ra)l(a)b(a)da=1. Earlier reproduction can change growth even when expected lifetime offspring are unchanged.
Values and equations
Σ_{x≥1}λ^(−x)l_xm_x=1; ∫₀∞e^(−ra)l(a)b(a)da=1; λ=e^(rΔt)
- λ,l_x,m_x,l(a)
- growth factor, discrete survival, pulse fecundity and continuous survival 1
- x
- discrete age in census intervals 1
- a,Δt
- continuous age and chosen time interval time unit
- b(a),r
- daughter production rate and exponential growth rate time-unit⁻¹
Conditions and scope
- Nonnegative survival and reproduction, positive reproduction at positive ages, convergent expressions and a consistently specified closed stationary environment; λ relates to r by λ=e^(rΔt) for the chosen time interval.
- A primitive nonnegative projection matrix has a stable asymptotic age distribution. Periodic, reducible, spatially heterogeneous, stochastic or density-dependent populations need the corresponding broader model; a transient population need not already grow at its asymptotic rate.
Sources · 2
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
- Lectures on Theoretical Ecology, §§5.1 and6.1: census conventions, survival and Euler–LotkaStephen P. Ellner — Cornell University (2009)Reference guide · PDF
- The evolution of life histories in spatially heterogeneous environments, equation1 and its homogeneous-environment limitsTadeusz J. Kawecki and Stephen C. Stearns (1993)Reference guide · PDF
Evidence and review
Read Ellner equations5.7–5.8, power-positive projection condition and6.11–6.13, and the original paper's explicit spatial limitation. Timing implication follows directly from the discounted reproduction sum. Excluded the notes' unconditional existence claim for every possible fertility distribution.
2026-10-10 · Independent AI editorial review: All six exact compact records, equations/variables/conditions and eighteen origin edges, plus actual bounded primary sections/abstracts listed below. This is independent AI editorial review, not laboratory validation or whole-Biology revalidation. Receipt: biology-quantitative-independent-review.1.
Entry details
Permanent link to this entry ↗- Record identity
- uni-bio-age-growth-equation
- Revision
- core.1
- Structured reference record
- University core expansion