Theoretical Ecology

, Volume 5, Issue 2, pp 297–309

Demographic heterogeneity impacts density-dependent population dynamics

  • Joseph P. Stover
  • Bruce E. Kendall
  • Gordon A. Fox
Original paper

DOI: 10.1007/s12080-011-0129-x

Cite this article as:
Stover, J.P., Kendall, B.E. & Fox, G.A. Theor Ecol (2012) 5: 297. doi:10.1007/s12080-011-0129-x

Abstract

Among-individual variation in vital parameters such as birth and death rates that is unrelated to age, stage, sex, or environmental fluctuations is referred to as demographic heterogeneity. This kind of heterogeneity is prevalent in ecological populations, but is almost always left out of models. Demographic heterogeneity has been shown to affect demographic stochasticity in small populations and to increase growth rates for density-independent populations. The latter is due to “cohort selection,” where the most frail individuals die out first, lowering the cohort’s average mortality as it ages. The importance of cohort selection to population dynamics has only recently been recognized. We use a continuous-time model with density dependence, based on the logistic equation, to study the effects of demographic heterogeneity in mortality and reproduction. Reproductive heterogeneity is introduced in three ways: parent fertility, offspring viability, and parent–offspring correlation. We find that both the low-density growth rate and the equilibrium population size increase as the magnitude of mortality heterogeneity increases or as parent–offspring phenotypic correlation increases. Population dynamics are affected by complex interactions among the different types of heterogeneity, and trade-off scenarios are examined which can sometimes reverse the effect of increased heterogeneity. We show that there are a number of different homogeneous approximations to heterogeneous models, but all fail to capture important parts of the dynamics of the full model.

Keywords

Demographic heterogeneity Individual variation Frailty Cohort selection Logistic model 

Copyright information

© Springer Science+Business Media B.V. 2011

Authors and Affiliations

  • Joseph P. Stover
    • 1
  • Bruce E. Kendall
    • 2
  • Gordon A. Fox
    • 3
  1. 1.Earth Research InstituteUniversity of CaliforniaSanta BarbaraUSA
  2. 2.Bren School of Environmental Science & ManagementUniversity of CaliforniaSanta BarbaraUSA
  3. 3.Department of Integrative BiologyUniversity of South FloridaTampaUSA

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