Evolution of indefinite generation lengths
Evolution of indefinite generation lengths
Intrinsic mortality at relatively advanced age results from natural selection favouring early reproduction. When individuals produce many and early offspring, costs are incurred due to the accumulation of pleiotropic mutations with adverse effects late in life, which make senescence an inevitable result of evolution. However, a few organisms exist with seemingly indefinite generation lengths. This paper identifies conditions of life history and ecology under which natural selection favours continually reducing intrinsic mortality. The analysis considers the particular case of populations held at carrying capacity by density dependence suppressing net fertility, acting either on fecundity equally across fecund ages or on juvenile mortality up to the first fecund age. This broad category of density dependence
increases the susceptibility of populations to invasion by mutations that extend net fertility into later life. Whether a population then evolves longer generation times depends on the relative timing of period benefit to onset of senescent cost amongst antagonistic pleiotropisms that arise to confront the selection process. Simulations show that if the onset of senescent costs either precedes the benefit, is concurrent with it, or is postponed by a fixed interval, then natural selection will favour those pleiotropisms that increase generation length. The selection on generation-lengthening pleiotropisms continues indefinitely and regardless of current generation length, for as long as the environment remains constant. The wide range of life histories encompassed by these conditions leads to the conclusion that many species may have evolved generation lengths considerably longer than the minimum set by developmental constraints.
ageing, immortality, iteroparity, k-selection, life history, life span, negligible senescence, semelparity
269-280
Doncaster, C. Patrick
0eff2f42-fa0a-4e35-b6ac-475ad3482047
October 2003
Doncaster, C. Patrick
0eff2f42-fa0a-4e35-b6ac-475ad3482047
Abstract
Intrinsic mortality at relatively advanced age results from natural selection favouring early reproduction. When individuals produce many and early offspring, costs are incurred due to the accumulation of pleiotropic mutations with adverse effects late in life, which make senescence an inevitable result of evolution. However, a few organisms exist with seemingly indefinite generation lengths. This paper identifies conditions of life history and ecology under which natural selection favours continually reducing intrinsic mortality. The analysis considers the particular case of populations held at carrying capacity by density dependence suppressing net fertility, acting either on fecundity equally across fecund ages or on juvenile mortality up to the first fecund age. This broad category of density dependence
increases the susceptibility of populations to invasion by mutations that extend net fertility into later life. Whether a population then evolves longer generation times depends on the relative timing of period benefit to onset of senescent cost amongst antagonistic pleiotropisms that arise to confront the selection process. Simulations show that if the onset of senescent costs either precedes the benefit, is concurrent with it, or is postponed by a fixed interval, then natural selection will favour those pleiotropisms that increase generation length. The selection on generation-lengthening pleiotropisms continues indefinitely and regardless of current generation length, for as long as the environment remains constant. The wide range of life histories encompassed by these conditions leads to the conclusion that many species may have evolved generation lengths considerably longer than the minimum set by developmental constraints.
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Published date: October 2003
Keywords:
ageing, immortality, iteroparity, k-selection, life history, life span, negligible senescence, semelparity
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Local EPrints ID: 35564
URI: http://eprints.soton.ac.uk/id/eprint/35564
ISSN: 0024-4066
PURE UUID: 0a7fc707-b848-4d05-b90b-b4aaccf8d4e2
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Date deposited: 19 May 2006
Last modified: 16 Mar 2024 02:49
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