Premium
The Statistical Analysis of Population Growth Rates Calculated from Schedules of Survivorship and Fecunidity
Author(s) -
Lenski Richard E.,
Service Philip M.
Publication year - 1982
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.2307/1936785
Subject(s) - survivorship curve , population growth , ecology , population , demography , geography , biology , sociology
Population growth rates can be estimated from sample cohort schedules of survivorship and fecundity, but the variation inherent in these estimates has received little attention. We define an ideal population such that it is completely described by the probabilities governing age—specific survival and reproduction. We define the lifetime contribution of an individual to population growth in a manner analogous to Fisher's (1931) reproductive values. The mean of these individual contributions is equal to the finite rate of increase for the population. We then investigate the properties of sample cohorts drawn from an ideal population. Estimates of population growth rates that are based on sample cohorts are shown to be biased. The magnitude of the bias decreases as the number of individuals used to construct the sample schedules of survivorship and fecundity is increased. This relationship conflicts with the statistical desirability of maximizing the number of estimates of the population growth rate. Bias can be reduced by pooling individual schedules to calculate a single estimate of the growth rate of the population within which individual contributions are defined. When cohort size is small, we recommend a modified jackknifing procedure for further reducing bias. To demonstrate the application of these methods, we obtain a 95% confidence interval for a rate of increased based on a sample cohort of aphids.