Figure 3

Parasite prevalence under control of Parasite 1 and allowing for bi-directionality in their effect. P2 and co-infection are the solid and broken lines on the left y-axis, P1 is the thick black line on the right y-axis; the x-axis is the fold reduction in Parasite 1 infection duration. The effect of Parasite 1 on Parasite 2 is depicted by the four larger quadrants: A) P1 reduces both host susceptibility to, and fecundity of, P2 (−/−); B) P1 reduces host susceptibility to, but increases fecundity of, P2 (−/+); C) P1 increases host susceptibility to, but reduces fecundity of, P2 (+/−); D) P1 increases host susceptibility to, and increases fecundity of, P2 (+/+). The equivalent effect of Parasite 2 on Parasite 1 is represented in the smaller sub-plots (respectively i, ii, iii and iv).