Data for: Non-host species reduce parasite infection in a focal host species within experimental fish communities

The dilution effect describes the negative association between host
biodiversity and the risk of infectious disease. Tests designed to
understand the relative roles of host species richness, host species
identity, and rates of exposure within experimental host communities would
help resolve ongoing contention regarding the importance and generality of
dilution effects. We exposed fathead minnows to infective larvae of the
trematode, Ornithodiplostomum ptychocheilus in minnow-only containers and
in mixed containers that held 1-3 other species of fish. Parasite
infection was estimated as the numbers of encysted worms (i.e.,
brainworms) present in minnows following exposure. The results of exposure
trials showed that non-minnow fish species were incompatible with O.
ptychocheilus larvae. There was no reduction in mean brainworm counts in
minnows in mixed containers with brook sticklebacks or longnose dace. In
contrast, brainworm counts in minnows declined by 51% and 27% in mesocosms
and aquaria, respectively, when they co-occurred with emerald shiners.
Dilution within minnow + shiner containers may arise from shiner-induced
alterations in minnow or parasite behaviours that reduced encounter rates
between minnows and parasite larvae. Alternatively, shiners may act as
parasite sinks for parasite larvae. These results highlight the role of
host-species identity in the dilution effect. Our results also emphasize
the complex and idiosyncratic effects of host community composition on
rates of parasite infection within contemporary host communities that
contain combinations of introduced and native species.