chesson: Two-species model of the storage effect
In primer: Functions and Data for the Book, a Primer of Ecology with R

Description Usage Arguments Details Value Author(s) References See Also Examples

Simulates a fluctuating environment over time, and two species' responses to the environment, after Chesson (1994).

chesson(
  alpha = c(1.1 * 1e-05, 1e-05),
  d = 0.1,
  years = 10,
  N0 = c(1000, 1e+05),
  w = c(0.6, 1),
  env.var = 1,
  specialization = 1,
  spread = 0.67,
  type = 1
)

`alpha`	a vector of length 2; the negative effects of all individuals (of both species) on each population – typically different among species.
`d`	disturbance rate; the proportion of all individuals killed at each time step.
`years`	numbers of time steps
`N0`	vector of length 2; initial abundances.
`w`	vector of length 2; average fitnesses for each species.
`env.var`	degree of environmental variability.
`specialization`	determines the narrowness of each species fitness response.
`spread`	determines how far apart the peak fitness responses are.
`type`	determines the form of C, the negative effect of competition.

The argument type controls the value of e^C, the effect of competition on reproduction, where the annual finite rate of increase is R=e^(E-C). type = 1 causes e^C = alpha[i] N[J,i], that is, a species-specific fixed fraction of juveniles that depends on each species response to competition. This is illustrated in a for-loop in Stevens (2009, Ch. 9, Storage Effect, Simulating Dynamics). Any other value for type results in the same negative effect on both species that depends on the number of juveniles and the disturbance rate.

Returns a list of length one, for use with ode in the deSolve package.

Component 1

vector of the state variables, y.

Hank Stevens (HankStevens@miamioh.edu)

Chesson, P.L. (1994) Multispecies competition in variable environments. Theoretical Population Biology, 45, 227–276.

Stevens. M.H.H. (2009) A Primer of Ecology with R. Use R! Series. Springer.

succniche

out <- chesson(years=50)
layout(matrix(1:4, nc=2))
matplot(out[["time"]], out[["Ns"]], type='l', lty=c(1:3),
        xlab="Time", ylab="N", log="y")
plot(out[["time"]][-1], out[["env"]], type='l',
     xlab="Time", ylab="Environment")
matplot(out[["env"]], out[["Es"]], xlab="Environment",
 ylab="Density-independent reproduction")
matplot(out[["env"]], out[["Rs"]], xlab="Environment",
 ylab="Annual growth rate")