ranlogist: Random Logistic Population Growth

In jarioksa/ecostudy: Ecology Teaching Package

Random Logistic Population Growth

Description

Random population growth with logistic expectation.

Usage

ranlogist(N0, b, d, K, bcontr=0.5)
## S3 method for class 'ranlogist'
plot(x, ...)
## S3 method for class 'ranlogist'
lines(x, ...)
## S3 method for class 'ranlogist'
traj(x, ...)

Arguments

N0	Initial population size
b	Birth rate.
d	Death rate.
K	Carrying capacity.
bcontr	The proportion of decrease of growth rate due to decrease in the birth rate.
x	"ranlogist" result object.
...	Other parameters passed to graphical functions.

Details

The stochastic population growth rate is based on logistic expectation following Pielou (1969). The instantaneous growth rate is the difference of birth and death rates r = b - d. The birth and death rates are dependent on current population size and at carrying capacity K they are equal (r = b). The sum of death and birth rates at given population size gives the current event rate which is used to simulate the time to the next event from exponential distribution. The next event is either (1) a birth that increases population size by one or (2) a death that reduces population size by one individual. Consequently, the population size is discrete (integer) but time is continuous, unlike in many other stochastic models which treat time as discrete, but population size as continuous. Further, Pielou's model has real temporal autocorrelation of population size, unlike many other models which vary expected population growth with no autocorrelation.

Krebs (2009, p. 155) discusses Pielou (1969) briefly, but ignores the advanced features of her model.

Function ranlogist perform the simulation, traj extracts the simulation results, and plot and lines can be used for graphics. The plot is based on plot.traj.

Value

Function ranlogist returns the model parameters, r, targeted end time of simulation (timend) and the simulation results in vectors time and N, and the function call.

Author(s)

Jari Oksanen

References

Krebs, C. J. (2009) Ecology. Benjamin Cummings. 6 ed., 655 pp.

Pielou, E.C. (1969) An Introduction to Mathematical Ecology. Wiley-Interscience, 286 pp.

Examples

par(mfrow=c(2,2))
replicate(4, plot(ranlogist(5, 1.2, 0.8, 50)))
par(mfrow=c(1,1))

jarioksa/ecostudy documentation built on June 27, 2022, 6:03 a.m.