Distributions of data lengths resulting from random permutations of galler enemy communities in relation to the galler phylogeny. The histograms show the distributions of data lengths when qualitative (i.e., presence/absence) data on enemy species are used instead of the quantitative rates of mortality used in Figure 3. In (A) and (B), the arrow indicates the length of the observed qualitative parasitism data, as calculated on the basis of the galler topology in Figure 2. (A) Distribution of data lengths when enemy communities (rows) are permuted 10000 times across the whole galler phylogeny (p < 0.0001). (B) Distribution of data lengths when enemy complexes are similarly permuted within gall-type groups (p = 0.0158). (C) Distribution of the difference in the absolute change in data length when the enemy complex of a galler species is replaced by those of two species from another gall type, of which only one also has a different host willow (see Methods). Negative values of the difference indicate that the change in data length is smaller when the replacing species occurs on the same host plant (paired samples t test, t = -4.93, 95% c.i. -∞ to -0.174, one-tailed p < 0.001).