The University of Colorado at Boulder study showed American toads who lived with gray tree frogs reduced their chances of parasitic infections known to cause limb malformations.

Researchers say their findings have strong implications for the benefits of biodiversity on emerging wildlife diseases.

The scientists said their experiments showed when toad tadpoles were raised in tanks with parasitic trematodes -- tiny worms whose larvae burrow into tadpole limb regions disrupting normal leg development -- 40 percent of the emerging frogs became deformed. But when toad tadpoles were joined in the tanks by gray tree frog tadpoles, the rate of parasitic infections dropped by nearly half.

"This is one of the first experimental studies to definitively show that an increase in diversity of host species actually can reduce parasite transmission and disease," said Assistant Professor Pieter Johnson.

The research appears in the journal Ecology Letters.