• DOI:10.1086/282877
• Corpus ID: 83561052

Life-History Consequences of Natural Selection: Cole's Result Revisited

@article{Charnov1973LifeHistoryCO,
  title={Life-History Consequences of Natural Selection: Cole's Result Revisited},
  author={Eric L. Charnov and William M. Schaffer},
  journal={The American Naturalist},
  year={1973},
  volume={107},
  pages={791 - 793}
}

• E. Charnov, W. Schaffer
• Published 1 November 1973
• Biology
• The American Naturalist

In his interesting paper on life-history strategies, Cole (1954) argued for the following result: "For an annual species, the absolute gain in intrinsic population growth that can be achieved by changing to the perennial reproductive habit would be exactly equivalent to adding one more individual to the average litter size." Thus, a clutch of size 101 at age 1 would serve the same purpose as having a clutch of size 100 every year forever. Gadgil and Bossert (1970) claimed that this was due to Cole's unrealistic assumption of no mortality during the life cycle, but Bryant (1971) proved the identical result with mortality present. This again raises the question of why there should be perennials. In this note we shall prove some general results (of which Cole's and Bryant's are special cases) to give at least one answer to this. Suppose we have two species, one an annual, the other a perennial. Both breed at the end of the first year and produce Ba and Bp offspring per individual, respectively. The proportion of offspring surviving the first year is C. Furthermore, the perennials have an adult survival rate of P per year. If N(T) is the number of organisms present in year T, counted just before reproduction but after the year's mortality, the rate of population growth (X) is given by: