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Effect of extrinsic mortality on the evolution of senescence in guppies


Classical theories1,2 for the evolution of senescence predict that organisms that experience low mortality rates attributable to external factors, such as disease or predation, will evolve a later onset of senescence. Here we use patterns of senescence in guppies derived from natural populations that differ in mortality risk to evaluate the generality of these predictions. We have previously found that populations experiencing higher mortality rates evolve earlier maturity and invest more in reproduction, as predicted by evolutionary theory3. We report here that these same populations do not have an earlier onset of senescence with respect to either mortality or reproduction but do with respect to swimming performance, which assesses neuromuscular function. This mosaic pattern of senescence challenges the generality of the association between decreased extrinsic mortality and delayed senescence and invites consideration of more derived theories for the evolution of senescence.

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The authors declare that they have no competing financial interests.


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This research was supported by NSF Grant and by the Academic Senate of the University of California. We thank P. Abrams, A. Bronikowski, M. Clark and P. Williams for comments on the manuscript.

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Competing interests

The authors declare that they have no competing financial interests.

Correspondence to David N. Reznick.

Supplementary information

Supplementary Discussion 1

Details of the comparison of the exponential and Gompertz fits to the age at last reproduction and age at death. (DOC 55 kb)

Supplementary Figure 1

Survivorship curves and plots of the natural log of mortality rate (y-axis) versus the log of the age at death (x-axis). (DOC 1082 kb)

Supplementary Discussion 2

A small pilot study on a third population (El Cedro River) of Trinidadian guppies reveals a parallel pattern of senescence. (DOC 52 kb)

Supplementary Discussion 3

Age-specific reproductive value as a function of age was compared between populations. (DOC 39 kb)

Supplementary Figure 2

Senescence as measured by age-specific reproductive value. (DOC 68 kb)

Supplementary Discussion 4

Rate of increase in fecundity with age in guppies from high and low predation environments. (DOC 24 kb)

Supplementary Figure 3

Age-specific fecundity in high and low predation guppies from natural populations. (DOC 121 kb)

Supplementary Methods

Details on the estimation of fecundity functions and reproductive value. (DOC 28 kb)

Supplementary Figure 4

An example of residual analysis using one combination from the Oropuche drainage. (DOC 53 kb)

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Further reading

Figure 1: Age at last reproduction.
Figure 2: Fecundity.
Figure 3: Maximum acceleration.


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