Data from: Partitioning the net effect of host diversity on an emerging amphibian pathogen

The ‘dilution effect’ (DE) hypothesis predicts that diverse host
communities will show reduced disease. The underlying causes of pathogen
dilution are complex, because they involve non-additive (driven by host
interactions and differential habitat use) and additive (controlled by
host species composition) mechanisms. Here, we used measures of
complementarity and selection traditionally employed in the field of
biodiversity–ecosystem function (BEF) to quantify the net effect of host
diversity on disease dynamics of the amphibian-killing fungus
Batrachochytrium dendrobatidis (Bd). Complementarity occurs when average
infection load in diverse host assemblages departs from that of each
component species in uniform populations. Selection measures the
disproportionate impact of a particular species in diverse assemblages
compared with its performance in uniform populations, and therefore has
strong additive and non-additive properties. We experimentally infected
tropical amphibian species of varying life histories, in single- and
multi-host treatments, and measured individual Bd infection loads. Host
diversity reduced Bd infection in amphibians through a mechanism analogous
to complementarity (sensu BEF), potentially by reducing shared habitat use
and transmission among hosts. Additionally, the selection component
indicated that one particular terrestrial species showed reduced infection
loads in diverse assemblages at the expense of neighbouring aquatic hosts
becoming heavily infected. By partitioning components of diversity, our
findings underscore the importance of additive and non-additive mechanisms
underlying the DE.