a, b, A few examples can be used to illustrate the joint influences of focal host abundance and the presence of close relatives on disease. Most of the most common species, for example, Avena barbata (Ab), Bromus diandrus (Bd), Raphanus raphanistrum (Rr) and Geranium dissectum (Gd), experienced high levels of diseased tissue, regardless of the identity of their neighbours (a, b, yellow circles). In contrast, although both Medicago polymorpha (Mp) and Taraxacum campylodes (Tc) were very rare (a, blue diamonds), T. campylodes experienced three times as much disease as M. polymorpha, perhaps because it had many more close relatives in the local community (b). Similarly, Convolvulus arvensis (Ca) and Sonchus asper (Sa) were found at the same abundance (a, red squares), but S. asper had more close relatives than C. arvensis (b) and experienced over four times as much disease. At intermediate abundance, Eschscholzia californica (Ec) and Nassella pulchra (Np) had very similar cover, but the latter suffered more than six times as much disease as the former (a, green triangles). Again, the species with more disease co-occurred with several close relatives while the relatively disease-free species was phylogenetically isolated (b). Note that axes are on a log scale.