Skip to main content
Open Access Publications from the University of California

UC Irvine

UC Irvine Previously Published Works bannerUC Irvine

Dynamics of single-species population growth: Experimental and statistical analysis


The logistic model, widely used for describing population growth, assumes that the per-capita rate of growth linearly decreases as the population size increases. Experimental data, however, suggest that often the per-capita rate of growth is not linearly related to population density. The theta model removes such linearity assumption by means of an additional parameter, θ; when θ = 1, the theta model reduces to the logistic model. We advance a method, the "jackknife" statistic, for estimating the rate of population growth (the largest eigenvalue and its variance) in the serial transfer system. Also, we propose a statistical method, PRESS, for quantifying the success of a given model in fitting experimental data. The criterion of success is the ability of a model to predict accurately new observations. One advantage of PRESS is that, contrary to what happens with other statistics such as R2, it tends to make a model less successful as the number of parameters increases (unless there is a disproportionate decrease in the bias of the new model). We have studied the rate of population growth in 25 genetically different populations of Drosophila melanogaster. The theta model provides a consistently better description of population growth in these populations than the logistic model. Moreover, the results indicate that the rate of growth is affected by the genetic constitution of a population. © 1981.

Many UC-authored scholarly publications are freely available on this site because of the UC's open access policies. Let us know how this access is important for you.

Main Content
For improved accessibility of PDF content, download the file to your device.
Current View