Data from: Phylogenetic structure and host abundance drive disease pressure in communities

Pathogens play an important part in shaping the structure and dynamics of
natural communities, because species are not affected by them equally. A
shared goal of ecology and epidemiology is to predict when a species is
most vulnerable to disease. A leading hypothesis asserts that the impact
of disease should increase with host abundance, producing a ‘rare-species
advantage. However, the impact of a pathogen may be decoupled from host
abundance, because most pathogens infect more than one species, leading to
pathogen spillover onto closely related species. Here we show that the
phylogenetic and ecological structure of the surrounding community can be
important predictors of disease pressure. We found that the amount of
tissue lost to disease increased with the relative abundance of a species
across a grassland plant community, and that this rare-species advantage
had an additional phylogenetic component: disease pressure was stronger on
species with many close relatives. We used a global model of pathogen
sharing as a function of relatedness between hosts, which provided a
robust predictor of relative disease pressure at the local scale. In our
grassland, the total amount of disease was most accurately explained not
by the abundance of the focal host alone, but by the abundance of all
species in the community weighted by their phylogenetic distance to the
host. Furthermore, the model strongly predicted observed disease pressure
for 44 novel host species we introduced experimentally to our study site,
providing evidence for a mechanism to explain why phylogenetically rare
species are more likely to become invasive when introduced. Our results
demonstrate how the phylogenetic and ecological structure of communities
can have a key role in disease dynamics, with implications for the
maintenance of biodiversity, biotic resistance against introduced weeds,
and the success of managed plants in agriculture and forestry.