Density dependence triggers runaway selection of reduced senescence

Seymour, Robert M. and Doncaster, C. Patrick (2007) Density dependence triggers runaway selection of reduced senescence PLoS Computational Biology, 3, (12), pp. 2580-2589. (doi:10.1371/journal.pcbi.0030256).


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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.

Item Type: Article
Digital Object Identifier (DOI): doi:10.1371/journal.pcbi.0030256
Additional Information: A previous version of this article appeared as an Early Online Release on November 14, 2007
ISSNs: 1553-734X (print)
Subjects: Q Science > QA Mathematics > QA75 Electronic computers. Computer science
Q Science > QH Natural history > QH301 Biology
ePrint ID: 50045
Date :
Date Event
18 June 2007Submitted
28 December 2007Published
Date Deposited: 17 Jan 2008
Last Modified: 16 Apr 2017 18:14
Further Information:Google Scholar

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