What began more than 50 years ago as a way to improve fishing bait in California has led a University of Tennessee researcher to a significant finding about how animal species interact that raises important questions about conservation.

In the middle of the 20th century, fishermen who relied on baby salamanders as bait introduced a new species of salamander to California water bodies. These Barred Tiger salamanders came into contact with the native California Tiger salamanders, and over time the two species began to mate.

"To give you a sense of the difference between these two species, they are about as closely related as humans and chimpanzees," said Ben Fitzpatrick, UT assistant professor.  said UT assistant professor Ben Fitzpatrick, a faculty member in the department of ecology and evolutionary biology.

Mating between two different species creates a hybrid offspring. According to Fitzpatrick, while such hybrids have been found to be successful in plant species, research has generally shown that animal hybrids cannot sustain themselves.

That is why it is surprising that these new hybrid salamanders were not only surviving but actually thriving in some cases.

"I thought I was studying hybrid dysfunction going into this study -- looking at how hybrids go wrong," said Fitzpatrick. "The level of vigor in these hybrids was completely unexpected."

Their research is among the first to show hybrid vigor among animal species, and Fitzpatrick noted that the work raises a number of questions for conservationists.

The California Tiger salamander is listed as a threatened species, but the Barred Tiger Salamander is not. The researchers predict that eventually all California Tiger salamanders will have some non-native genes.

Is this beneficial to the native species? Fitzpatrick says that depends on how conservationists choose to define the new hybrid.

"If they consider it an acceptable modification of the original species, then this could enhance the chances for survival of the California Tiger salamander," he said, "but others may consider the hybrids to be genetically impure and see hybridization as accelerating extinction."

It is not yet clear from the research what is causing the hybrids to thrive.

Fitzpatrick and colleagues plan to broaden their study of these salamanders and to explore the implications for other animals in their ecosystem.

"We're right at the front in thinking that these ideas may be much more generally applicable," he said. He pointed to two other studies in recent months that have explored the issue of hybridization in butterflies.

Fitzpatrick is also doing research in East Tennessee caves examining the interactions between spring salamanders and the official state amphibian the Tennessee Cave salamander.