Observatory: Hybrid species can be disastrous for natives

The ecological effects of invasive species are often well known, particularly their impact on native plants or animals. But the invaders sometimes make love as well as war: they mate with related local species, producing hybrids. And the effects of such hybridization have not been the subject of much study. Now, research involving invasive and native salamanders in the Salinas Valley of California shows how devastating this can be: the hybrids have voracious appetites and can practically wipe out other species. Maureen E. Ryan and Jarrett R. Johnson of the University of California, Davis, and Benjamin M. Fitzpatrick of the University of Tennessee studied hybrids between native California tiger salamanders and barred tiger salamanders, brought in huge numbers from Texas beginning 60 years ago by California bait dealers. Tiger salamander larvae are high on a pond's food chain, gulping down larvae of other species with their big mouths. The researchers built artificial ponds, stocked them with salamanders and other species, notably the California newt and the Pacific chorus frog (both of which are found in the Salinas Valley) and monitored what happened. Their findings appear in The Proceedings of the National Academy of Sciences. Hybrid larvae had a greater effect on the newts and frogs than native salamander larvae did, nearly wiping them out. Hybrids even affected the survival of native salamanders in the ponds. "The implication is they're ecologically quite different than the native species," Ms. Ryan said. That could spell trouble for other "third-party" species in the valley, like the California red-legged frog and the Santa Cruz long-toed salamander.