Fig. 5

Stable coexistence of two consumers and two resources. The system first moves to the trivial equilibrium, the supply point, with only the resources, indicated by the blue dot in the phase plot (b). Next it develops to the point where only B is present, which (also) is a saddle point. Finally in a, b a stable coexistence of the consumers is reached at the intersection of the zero growth isoclines of A (magenta) and B (blue). The thin dashed lines indicate the consumption vectors of the two consumers. In c, d the initial density of species A is zero. Now the system behaves effectively as that of a single consumer and two resources. The resources quickly obtain their stable level, almost that is, since there still is a minute amount of consumer. Once consumption starts in earnest, both resources disappear in the ratio of the consumption vector of B, and an unstable state is reached, grace to the strict absence of A. In e, f the initial density of species B is set to zero. The system moves again to the trivial state, but next develops parallel to the consumption vector of A to the saddle point with only this species present. Since the initial density of A is quite low, the trivial state is approached very closely and in fact seems to be stable for a short time interval, until the density of A is sufficient to show it is a saddle point indeed