Hybrid salamanders don't follow theory

DAVIS, Calif., Sept. 27 (UPI) -- A finding of a U.S. study of hybrid salamanders has contradicted prevailing scientific theory about what happens when animal species interbreed.

The University of California-Davis research conducted by Professor Bradley Shaffer and former doctoral student Benjamin Fitzpatrick focused on survival rates and genetic makeup of three types of salamanders: native California tiger salamanders, an endangered species; barred tiger salamanders that were introduced in California from Texas in the 1950s; and the hybrid offspring of the two species.

The researchers discovered more of the hybrid young survived in the wild than did young of the native or the introduced species. Prevailing theory suggests animal hybrids are less fit than their parents, with so-called "hybrid vigor" largely limited to plant crosses.

Shaffer said the finding raises difficult questions for managing endangered native salamander populations, since some conservationists believe hybrids are favored by natural selection and "improve" the original species. Others might consider hybrids to be genetically impure and regard them as threats to the native salamanders, their competitors and their prey.

The study appeared recently in the online edition of the Proceedings of the National Academy of Sciences.

Copyright 2007 by United Press International

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