Data from: An experimental test of the transmission−virulence trade-off hypothesis in a plant virus

The transmission–virulence trade-off hypothesis is one of the few adaptive
explanations of virulence evolution, and assumes that there is an overall
positive correlation between parasite transmission and virulence. The
shape of the transmission–virulence relationship predicts whether
virulence should evolve toward either a maximum or to an intermediate
optimum. A positive correlation between each of these traits and
within-host growth is often suggested to underlie the relationship between
virulence and transmission. There are few experimental tests of this
hypothesis; this study reports on the first empirical test on a plant
pathogen. We infected Brassica rapa plants with nine natural isolates of
Cauliflower mosaic virus and then estimated three traits: transmission,
virulence, and within-host viral accumulation. As predicted by the
trade-off hypothesis, we observed a positive correlation between
transmission and virulence, suggestive of the existence of an intermediate
optimum. We discovered the unexpected existence of two groups of
within-host accumulation, differing by at least an order of magnitude.
When accumulation groups were not accounted for, within-host accumulation
was correlated neither to virulence nor transmission, although our results
suggest that within each group these correlations exist.