The vitality model: a way to understand population survival and demographic heterogeneity.
A four-parameter model describing mortality as the first passage of an abstract measure of survival capacity, vitality, is developed and used to explore four classic problems in demography: (1) medfly demographic paradox, (2) effect of diet restriction on longevity, (3) cross-life stage effects on survival curves and (4) mortality plateaus. The model quantifies the sources of mortality in these classical problems into vitality-dependent and independent parts, and characterizes the vitality-dependent part in terms of initial and evolving heterogeneities. Three temporal scales express the balance of these factors: a time scale of death from senescence, a time scale of accidental mortality and a crossover time between evolving vs. initial heterogeneity. The examples demonstrate how the first-passage approach provides a unique and informative perspective into the processes that shape the survival curves of populations.
Li
Ting
T
Quantitative Ecology and Resource Management, University of Washington, Box 352182, Seattle, WA 98195, United States.
Anderson
James J
JJ
D003710:Demography; D008962:Models, Theoretical; D011157:Population Dynamics