Figure 6.

Unsupervised simulation screen reveals a nested parameter space structure. Each point represents a sample from the Latin hypercube sample, so that each point has unique values of a, b, c, R_T, and ρ_T. Each panel shows a 3D projection of the 5D parameter space. (a–c) The LPA parameter screen reveals parameter space structure, with tristable polarizable (red) parameter sets nested inside bistable polarizable (yellow) parameter sets nested inside a large region of monostable polarizable (gray) parameter sets. Nonpolarizable monostable parameter sets are not plotted. These parameter sets would fill out the empty space in (a)–(c). (d–e) The PDE Parameter Screen confirms the parameter space structure predicted by the LPA (plotting conventions as in a–c). (g–i) For each tristable parameter set, the level of stimulus (none, small, large) required to elicit a polarization response from the coexistence HSS is shown. For yellow points, a stimulus double or half the value of the HSS active protein concentration yields a response. For black points, a stimulus greater than 10 times or one-tenth the value of the HSS concentration yields a response. When the coexistence HSS is LPA unstable (red points), any perturbation away from the coexistence HSS may result in polarization. Other parameters are s = 0.5 and n = 3. To see this figure in color, go online.