Survival-augmented Ricker map
= Survival-augmented Ricker map
The population iteration
$$
x_{n+1}=x_n\bigl(r+ke^{-\lambda x_n}\bigr),
\qquad 0\leq r<1,
$$
combines annual survival with density-dependent recruitment. Its positive equilibrium is
$$
x_*=\frac1\lambda\log\frac{k}{1-r},
$$
which exists when $k>1-r$.