Stage dynamics, period survival, and mortality plateaus

Carol C Horvitz, Shripad Tuljapurkar

Research output: Contribution to journalArticle

36 Citations (Scopus)

Abstract

Mortality plateaus at advanced ages have been found in many species, but their biological causes remain unclear. Here, we exploit age-from-stage methods for organisms with stage-structured demography to study cohort dynamics, obtaining age patterns of mortality by weighting one-period stage-specific survivals by expected age-specific stage structure. Cohort dynamics behave as a killed Markov process. Using as examples two African grasses, one pine tree, a temperate forest perennial herb, and a subtropical shrub in a hurricane-driven forest, we illustrate diverse patterns that may emerge. Age-specific mortality always reaches a plateau at advanced ages, but the plateau may be reached rapidly or slowly, and the trajectory may follow positive or negative senescence along the way. In variable environments, birth state influences mortality at early but not late ages, although its effect on the level of survivorship persists. A new parameter μω summarizes the risk of mortality averaged over the entire lifetime in a variable environment. Recent aging models for humans that employ nonobservable abstract states of "vitality" are also known to produce diverse trajectories and similar asymptotic behavior. We discuss connections, contrasts, and implications of our results to these models for the study of aging.

Original languageEnglish
Pages (from-to)203-215
Number of pages13
JournalAmerican Naturalist
Volume172
Issue number2
DOIs
StatePublished - Aug 1 2008

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plateaus
plateau
mortality
Survival
Mortality
trajectories
Cyclonic Storms
Markov Chains
Pinus
hurricanes
trajectory
temperate forests
Poaceae
cohort studies
demography
herbs
Cohort Studies
Survival Rate
shrubs
survival rate

Keywords

  • Age from stage
  • Cohort dynamics
  • Killed Markov processes
  • Long-run stochastic mortality rate

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Medicine(all)

Cite this

Stage dynamics, period survival, and mortality plateaus. / Horvitz, Carol C; Tuljapurkar, Shripad.

In: American Naturalist, Vol. 172, No. 2, 01.08.2008, p. 203-215.

Research output: Contribution to journalArticle

Horvitz, Carol C ; Tuljapurkar, Shripad. / Stage dynamics, period survival, and mortality plateaus. In: American Naturalist. 2008 ; Vol. 172, No. 2. pp. 203-215.
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