Theory suggests that a source-sink structure for a prey species can promote
the persistence of an otherwise nonpersisting predator-prey interaction. U
sing a heliozoan protist predator, Actinosphaerium nucleofilum, and a cilia
ted protozoan prey species, Tetrahymena pyriformis, we tested this predicti
on in laboratory microcosms. We created subdivided microcosms, each consist
ing of a 30-mL bottle containing predators and prey connected to a 30-mL bo
ttle containing prey only. Prey dispersed freely through this connection, b
ut predators did not disperse for hundreds of prey generations. The predato
rs and prey in the subdivided microcosms persisted for over three times as
long as they did in undivided 30-mL and 60-mL bottles. Our results suggest
that prey rescue effects and spatial asynchrony in prey dynamics, character
istic metapopulation features, enhanced persistence in the subdivided micro
cosms. However, the details by which persistence was achieved closely resem
ble source-sink dynamics, not classic metapopulation dynamics. Evidence sug
gests that continuous prey immigration into predator-prey bottles from exti
nction-invulnerable prey-only bottles may have weakened the coupling betwee
n predator and prey dynamics and contributed to the increase in persistence
. In showing that source-sink dynamics enhanced predator-prey persistence,
our experiments support conclusions of metapopulation theory that point to
the importance of immigration between spatially discrete populations.