Figure 4. DCV virulence decreases in the absence of immune pathways.

DCV infectious stocks were prepared from viral passages P = 1 and P = 10 and from each fly genotype. w¹¹¹⁸ flies were intrathoracically inoculated with 10 TCID₅₀ units of each DCV stock and survival of the flies was measured daily. a) Survival curves shown in the figure are the combination of the two independent replicates, with three technical replicates each, of a total of at least N = 98 flies per treatment. Error bars indicate ± Standard error of the mean (SEM); n.s., not significant. Survival curves were compared via log-rank (Mantel–Cox) tests. b) Test of the contribution of historical contingency evolved (P = 10) vs ancestral (P = 1) DCV virulence. The dashed red line represents the linear regression, and the black line represents the expected relationship under the null hypothesis of ancestral differences in DCV virulence which are maintained after evolution despite noise introduced by random events (mutation and drift).