Graph A: Recessive Lethal NI. Bidirectional CI increases stability of nuclear divergence. The graph shows that the parameter plane is divided into four zones: (1) stable NI and loss bidirectional CI (orange), (2) stable NI and bidirectional CI (yellow), (3) loss of NI and stable bidirectional CI (blue), (4) loss of both NI and bidirectional CI (white). The dotted and solid lines indicate the critical migration rates of NI and bidirectional CI, respectively. Bidirectional CI is stable if both Wolbachia strains stably coexist. Parameters: l
NI = 1, h = 0, s = 0.1. Under these parameter values of strong recessive NI, presence of NI has little effect on CI stability, whereas CI level strongly effects stability of nuclear divergence. Graph B: Variable Dominance NI. Critical migration rates for nuclear divergence as functions of the CI level for h = 1 (triangles), h = 0.99 (circles), h = 0.5 (boxes) h = 0 (diamonds). Other parameters: l
NI = 1, s = 0.1. Whereas CI has no effect when lethality dominance is 1 (as expected), it has a large effect when even a low level of F1 hybrid survival occurs (h = 0.99).