Evol Ecol Res 16: 435-439 (2014)     Full PDF if your library subscribes.

Gompertz mortality, natural selection, and the ‘shape of ageing’

Eric L. Charnov

Department of Biology, The University of New Mexico, Albuquerque, New Mexico, USA

Correspondence: E.L. Charnov, Department of Biology, The University of New Mexico, Albuquerque, NM 87131, USA.
e-mail: rlc@unm.edu


Question: Proposals for measuring the shape of ageing are dimensionless comparisons of early adult mortality (Z0) with aggregate mortality over the adult lifespan. What do the shape parameters actually measure? And how do they relate to the optimal age/size at maturity?

Methods: Dimensional analysis is applied to an adult Gompertz mortality function, Zx = Z0ec · x. R0, fitness in non-growing populations, is maximized with respect to the age at maturity, α.

Conclusions: A constant value for any ‘shape of ageing’ number among a collection of species implies that they also have the same value for the ratio of the two Gompertz parameters, c/Z0 (if mortality is Gompertz). Z0 appears in both the shape measure(s) and the formula for the optimal α; this provides a link between the rate of ageing and the criterion for the initiation of reproductive maturation. This ESS result suggests that (perhaps) Z0, external mortality rate early in adulthood, and not any mass-specific physiological rate, should determine the ageing rate.

Keywords: rate of living, maturation, fish, senescence, mortality rate

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