Anonymous
Anonymous asked in Science & MathematicsBiology · 1 decade ago

# If the rmax is 0.50, the population size is 18 & the carrying capacity is 477.?

is the growth rate 86.4????

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• Anonymous

To estimate density dependence, you may want to perform a regression of R(t) [or r(t)=log(R(t))] on N(t), and use the y-intercept as the estimate of Rmax [or rmax], assuming it is a declining function.

However, note that N(t) appears both in the dependent and in the independent variable of the regression! This implies that if N(t) are measured with error (as they are in most cases), or are subject to other (stochastic) factors, then the estimate of the slope of the regression and, hence the estimate of Rmax, will be biased. In particular, if the data are from density-independent population fluctuations, you will often get an estimate of Rmax above 1.0, meaning that you will detect density dependence even though it does not exist.

For example, a time series produced by a density-independent, age-structured model with environmental stochasticity in survival rates and fecundities. The attempt to fit a simple density dependence model to this data. The line shows linear regression of population growth rate, ln(R), on population size, N. The population growth rate is calculated as ln(R(t)) = ln( N(t+1) / N(t) ). Even though the model that produced the data did not include density dependence, the negative slope of the regression line indicates density dependence, with an intercept of about 0.24, which corresponds to Rmax of about 1.3.