 Solution

Write $D=AB-1>0$. The physically nonnegative branches, omitting $S_1$, areOn both bifurcation diagrams, draw $S_2$ solid for $\gamma <B$ and dashed for $\gamma >B$; draw $S_3$ dashed for $\gamma <1/A$ and solid for $\gamma >1/A$. The coexistence branch $S_4$ is dashed throughout its interior because it is a saddle point. It connects $S_3$ at $\gamma =1/A$ to $S_2$ at $\gamma =B$, through two transcritical bifurcations when the branches are continued mathematically beyond the nonnegative quadrant.