Estimating Density Dependence, Environmental Variance, and Long-Term Selection on a Stage-Structured Life History

TY - JOUR

T1 - Estimating Density Dependence, Environmental Variance, and Long-Term Selection on a Stage-Structured Life History

AU - Lande, R.

AU - Grøtan, V.

AU - Engen, S.

AU - Visser, M. E.

AU - Sæther, B.-E.

N1 - Data archiving: Dryad; Code archiving Zenodo

PY - 2023/2/3

Y1 - 2023/2/3

N2 - A method for analyzing long-term demographic data on density-dependent stage-structured populations in a stochastic environment is derived to facilitate comparison of populations and species with different life histories. We assume that a weighted sum of stage abundances, N, exerts density dependence on stage-specific vital rates of survival and reproduction and that N has a small or moderate coefficient of variation. The dynamics of N are approximated as a univariate stochastic process governed by three key parameters: the density-independent growth rate, the net density dependence, and environmental variance in the life history. We show how to estimate the relative weighs of stages in N and the key parameters. Life history evolution represents a stochastic maximization of a simple function of the key parameters. The long-term selection gradient on the life history can be expressed as a vector of sensitivities of this function with respect to density-independent, density-dependent, and stochastic components of the vital rates. To illustrate the method, we analyze 38 years of demographic data on a great tit population, estimating the key parameters, which accurately predict the observed mean, coefficient of variation, and fluctuation rate of N; we also evaluate the long-term selection gradient on the life history.

AB - A method for analyzing long-term demographic data on density-dependent stage-structured populations in a stochastic environment is derived to facilitate comparison of populations and species with different life histories. We assume that a weighted sum of stage abundances, N, exerts density dependence on stage-specific vital rates of survival and reproduction and that N has a small or moderate coefficient of variation. The dynamics of N are approximated as a univariate stochastic process governed by three key parameters: the density-independent growth rate, the net density dependence, and environmental variance in the life history. We show how to estimate the relative weighs of stages in N and the key parameters. Life history evolution represents a stochastic maximization of a simple function of the key parameters. The long-term selection gradient on the life history can be expressed as a vector of sensitivities of this function with respect to density-independent, density-dependent, and stochastic components of the vital rates. To illustrate the method, we analyze 38 years of demographic data on a great tit population, estimating the key parameters, which accurately predict the observed mean, coefficient of variation, and fluctuation rate of N; we also evaluate the long-term selection gradient on the life history.

KW - demography

KW - density dependence

KW - environmental vari-ance

KW - great tit

KW - selection

KW - sensitivity

U2 - 10.1086/723211

DO - 10.1086/723211

M3 - Article

SN - 0003-0147

VL - 201

SP - 557

EP - 573

JO - American Naturalist

JF - American Naturalist

IS - 4

ER -