Figure 3.

Forest plots showing the distribution of effect sizes for virus–host categories. Forest plot showing the distributions of effect sizes for viruses infecting plants (a), animals (b), and bacteriophages (c). The diamond indicates the pooled correlations. Viruses that infect plants indicate an overall positive correlation, which implies a positive relationship between virulence and transmission (R = 0.44). Most plant viruses tested the evolution of virulence framework, except for datasets 7 and 8 which tested the generalism–specialism dichotomy. No datasets explored life history theory in this category. Viruses that infect animals represented negative correlations with a pooled correlation of R = −0.6429. This category had a reasonable distribution of datasets across all three frameworks. The evolution of virulence is represented by datasets 23, 24, 28, and 29. The life history theory category is represented by datasets 34, 35, 36, 37, 42, 43, while the generalism–specialism dichotomy is represented by datasets 30, 31, 32, 33, 38, 39, 40, and 41. The pooled correlation for bacteriophages is R = −0.35 with most datasets identified for the generalism–specialism dichotomy (datasets 48, 49, 50, 56, 57, 58, 59, and 60). The evolution of virulence is represented by datasets 45, 46, 47, 52 and 54, and life history theory represented by datasets 44, 51, 53, and 55.