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Density dependence triggers runaway selection of reduced senescence

By Robert M. Seymour and C. Patrick Doncaster

Abstract

In the presence of exogenous mortality risks, future reproduction by an individual is worth less than present reproduction to its fitness. Senescent aging thus results inevitably from transferring net fertility into younger ages. Some long-lived organisms appear to defy theory, however, presenting negligible senescence (e.g., hydra) and extended lifespans (e.g., Bristlecone Pine). Here, we investigate the possibility that the onset of vitality loss can be delayed indefinitely, even accepting the abundant evidence that reproduction is intrinsically costly to survival. For an environment with constant hazard, we establish that natural selection itself contributes to increasing density-dependent recruitment losses. We then develop a generalized model of accelerating vitality loss for analyzing fitness optima as a tradeoff between compression and spread in the age profile of net fertility. Across a realistic spectrum of senescent age profiles, density regulation of recruitment can trigger runaway selection for ever-reducing senescence. This novel prediction applies without requirement for special life-history characteristics such as indeterminate somatic growth or increasing fecundity with age. The evolution of nonsenescence from senescence is robust to the presence of exogenous adult mortality, which tends instead to increase the age-independent component of vitality loss. We simulate examples of runaway selection leading to negligible senescence and even intrinsic immortality

Topics: QA75, QH301
Year: 2007
OAI identifier: oai:eprints.soton.ac.uk:50045
Provided by: e-Prints Soton

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  1. (2005). Ageing and death in an organism that reproduces by morphologically symmetric division.
  2. (2000). Ageing and immortality.
  3. (1952). An unsolved problem in biology. London:
  4. (1976). Clone size in American aspens.
  5. (1980). Creosote bush: long-lived clones in the Mojave desert.
  6. (1995). Direct selection on life span in Drosophila melanogaster.
  7. (2001). Does bristlecone pine senesce?
  8. (1993). Does increased mortality favor the evolution of more rapid senescence?
  9. (1980). Ecological relationships of bristlecone pine.
  10. (2001). Effects of tree age on pollen, seed, and seedling characteristics in Great Basin bristlecone pine.
  11. (1994). Evolution in age-structured populations. 2nd edition. Cambridge (United Kingdom):
  12. (1977). Evolution of ageing.
  13. (2003). Evolution of indefinite generation lengths.
  14. (1991). Evolution of senescence: late survival sacrificed for reproduction.
  15. (2000). Evolution: an introduction.
  16. (1991). Evolutionary biology of ageing. Oxford (United Kingdom):
  17. (2007). Extrinsic mortality and the evolution of senescence.
  18. (1999). Free radicals in biology and medicine. 3rd edition. Oxford (United Kingdom):
  19. (2005). Hamilton’s indicators and the force of selection.
  20. (2005). Heritability and genetic constraints of life-history trait evolution in preindustrial humans.
  21. (2001). History and prospects: symposium on organisms with slow aging.
  22. (1992). How should we define fitness for general ecological scenarios?
  23. (2006). Inevitable senescence? Contributions to evolutionarydemographic theory [thesis]. London: University College London.
  24. (2002). Mechanisms of ageing: public or private?
  25. (1998). Mortality patterns suggest a lack of senescence in hydra.
  26. (1995). On evolutionarily stable life histories, optimization and the need to be specific about density dependence.
  27. (1996). On measuring the rate of ageing.
  28. (1970). On r- and K- selection.
  29. (1993). Optimality, mutation and the evolution of ageing.
  30. (1957). Pleiotropy, natural selection and the evolution of senescence.
  31. (2005). Population dynamics, life history, and demography: lessons from Drosophila.
  32. (1983). Population-dynamics and habitat suitability of the intertidal sea-anemones Anthopleura elegantissima and Anthopleura xanthogrammica.
  33. (2002). r- and K-selection revisited: the role of population regulation in life-history evolution.
  34. (2002). Recruitment limitation and population density in the harvester ant, Pogonomyrmex occidentalis.
  35. (1981). Repair and its evolution: survival versus reproduction. In: Townsend CR, Calow P. Physiological ecology: an evolutionary approach to resource use. Oxford (United Kingdom): Blackwell Scientific Publications.
  36. (1984). Restitution of r- and K-selection as a model of densitydependent natural selection.
  37. (1962). Some generalized theorems of natural selection.
  38. (2004). The case for negative senescence.
  39. (1992). The evolution of life histories. Oxford (United Kingdom):
  40. (1977). The evolution of life history traits: a critique of the theory and a review of the data.
  41. (1966). The moulding of senescence by natural selection.
  42. (2006). The shaping of senescence in the wild.
  43. (1967). The theory of island biogeography.
  44. (1997). Theoretical and empirical examination of densitydependent selection.
  45. Thorarinsdo ´ttir GG (2002) Abundance of ocean quahog, Arctica islandica, assessed by underwater photography and a hydraulic dredge.
  46. (1999). Time of our lives: the science of human ageing. London: Weidenfield and Nicolson.
  47. (2004). To age or not to age. Proc Roy Soc
  48. (2000). Why do we age?

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