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6 Toward an Evolutionary Demography
Pages 96-107

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From page 96...
... This situation has continued despite the parallel development of an evolutionary theory for life history, including aging, from the 1930s to the present (see Charlesworth, 1994~. On the one hand, we have the ad hoc models of demography, and on the other we have the a priori models of evolutionary theory.
From page 97...
... BASIC THEORY OF EVOLUTIONARY DEMOGRAPHY The fundamental starting point for evolutionary analysis is an ecologically determined demography: particular age-specific survival probabilities and fecundities, varying also with time, organismal size, population density, and a range of other factors (Charlesworth, 1994~. Frequently, however, factors other than age are neglected in the theory, and I will follow this practice for the sake of convenience and clarity.
From page 98...
... The foregoing should not be taken as a complete presentation of the theory of selection on age-structured populations, for which the best summary remains that of Charlesworth (1994~. EMPIRICAL EVIDENCE CONCERNING THE FORCE OF NATURAL SELECTION Unlike many other global theories in population biology, the basic evolutionary theory of demography leads to some directly testable theoretical predications.
From page 99...
... Island populations are exposed to less natural predation and suffer lower adult mortality rates, compared to mainland populations. Evolutionary theory predicts that the island populations should show slower aging.
From page 100...
... THEORETICAL POPULATION GENETICS OF LIFE-HISTORY EVOLUTION But the force of natural selection does not entirely determine the pattern of demographic evolution. An additional determinant is the nature of the genetic mechanisms that affect particular life-history characters.
From page 101...
... Fortunately, these corollaries are testable in experimental systems. EXPERIMENTAL POPULATION GENETICS OF LIFE-HISTORY EVOLUTION The first thing to be said about the experimental population genetics of life history is that additive genetic variation is maintained for a variety of demographic characters in a variety of species (Rose, 1991; Roff, 1992~.
From page 102...
... , and it certainly has much to recommend it, particularly in comparison with alternative indices, like mean or maximum life span, when the data are collected under dubious conditions. My colleagues at the University of California, Irvine, and I have recently explored the extent to which the Gompertz model can be used to predict accurately the demography of experimental Drosophila populations (Mueller et al., 1995; Nusbaum et al., 1996~.
From page 103...
... However, when the model is fitted using maximum-likelihood or nonlinear-regression methods, as opposed to conventional numerical approaches, we find that Gompertz parameters can be used to predict the mortality patterns of experimental populations of Drosophila after just 20-30 percent of the deaths of an observed cohort. The fit of these predictions can achieve respectable levels of accuracy, placing such parameters as mean longevity and 95 percent mortality within tight 95 percent confidence intervals.
From page 104...
... For these reasons, we have proceeded instead to develop a population genetics theory for demography. CONCLUSION Recent work on age-specific mortality rates strongly suggests that conventional demographic models are in need of repair.
From page 105...
... Pike, and M Witten 1990 Slow increases of the Gompertz mortality rate during aging in certain animals approximate that of hears.
From page 106...
... American Naturalist 123:565-569. 1985 Life history evolution with antagonistic pleiotropy and overlapping generations.
From page 107...
... Rose 1988 Multiple genetic mechanisms for the evolution of senescence in Drosophila melanogaster. Evolution 42:708-716.


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