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. 2016 Dec 13;7:13849. doi: 10.1038/ncomms13849

Figure 3. Interpreting the ESS virulence levels with a graphical method.

Figure 3

We use a graphical method similar to the one developed by van Baalen and Sabelis43 to determine which ESS virulence will be greater. (a) Comparison between the ESS virulence with and without vertical transmission in the absence of sex-specific strategies. Without vertical transmission (α=0) the ESS exploitation strategy (Inline graphic) is the point where the tangent of the horizontal transmission function (β′(δ)) crosses the abscissa in δ=0. With vertical transmission (α>0), the ESS exploitation strategy (Inline graphic) is the point where the tangent of the horizontal transmission function (β′(δ)) crosses the abscissa in Inline graphic. Notice that the tangent of the horizontal transmission function at the ESS is higher or equal with vertical transmission, that is Inline graphic. This implies that the ESS virulence is greater or equal without vertical transmission, that is Inline graphic. (b) Comparison between the ESS virulence when the virulence can differ in males and females. With male-specific virulence (Inline graphic) the ESS exploitation strategy (Inline graphic) is the point where the tangent of the horizontal transmission function crosses the abscissa in δm=0. With female-specific virulence (Inline graphic) the ESS exploitation strategy (Inline graphic) is the point where the tangent of the horizontal transmission function crosses the abscissa in Inline graphic. Notice that the tangent of the horizontal transmission function at the ESS is higher or equal with female-specific virulence, that is Inline graphic. This implies that the ESS virulence is greater or equal in males, Inline graphic.