Fig. 3.

Associations between ST1 (blue) and ST2 (green) with antigenic types ax, bx, ay, and by (representing the various epitope combinations possible within a two-locus, two-allele model) under strong immune selection. The different dynamic outcomes are each ST is uniquely associated with a dominant antigenic type (A), periodic replacement of antigenic type linked to a particular ST (B), and competitive exclusion of one ST (C). In this example, R₀ of ST1 = 5, R₀ of ST2 = 5.1 (A), 4.3 (B), and 4.05 (C). Other parameters used were: σ = 20.27 yr⁻¹, ς = 2.03 yr⁻¹, γ = 0.97. Population size = 1,000.