Levins: dp/dt=c·p(1−p)−e·p; p_ss=(c−e)/c; λ_p0=c−e; at c=2,e=1: p_ss=1/2

Sympy-exact symbolic witness of the Levins metapopulation canonical form and persistence-threshold anchors. Setup: p, c, e — all positive symbols. Levins ODE: dp/dt = c·p·(1−p) − e·p (sympy canonical '-c*p**2 + c*p - e*p' after expand;…