Fig. 4

A single consumer and two essential resources. In all cases the system first develops towards the trivial equilibrium, which is unstable. Once the consumer density starts increasing, both resource densities are lowered. The difference between the simulations a, b is the stable resource level of P, which is the limiting resource. A lower supply level in b reduces the supply rate of this resource, and hence the stationary level of the consumer. The stationary level of P is exactly the same. Since less of R is consumed, but the supply remains the same, it reaches a higher stationary level. In c, d the coexistence point is exactly the same as in (a), but the consumer death rate and resource growth rates are quite different. Now the coexistence point is a stable vortex, with the trajectory spiralling towards it. The time plot shows oscillating behaviour