From Sacramento Fish and Wildlife Office
Other primary threats are hybridization, or interbreeding, with non-native salamanders, and predation by non-native species. The threat of hybridization is particularly severe in the Central Coast Range and the Bay Area, and to a lesser extent the Central Valley.which indicates hybridization is a problem but doesn't speak to it's role in species formation.
From Evolution:
After an estimated five million years of independent evolution, the barred tiger salamander (Ambystoma tigrinum mavortium) was introduced by bait dealers into the native range of the California tiger salamander (A. californiense). Hybridization and backcrossing have been occurring in central California for 50–60 years, or an estimated 15–30 generations. (from the article abstract)
Also from here:
For many years, the tiger salamanders were considered a single polytypic species, A. tigrinum, that had the most widespread geographic distribution of any salamander species in North America. Molecular genetic studies (Shaffer, 1984; Routman, 1993; Templeton et al., 1995; Shaffer and McKnight, 1996) indicate that the tiger salamanders cannot be considered a single species and that the formally recognized subspecies may not be valid taxonomic units. Furthermore, A. tigrinum as currently recognized is paraphyletic with respect to numerous Mexican species, many of which are perennibranchiate forms having restricted geographic distributions. Evolution of perennibranchiate forms probably has occurred numerous times from within the A. tigrinum complex.
This article has interesting info also.
Unfortunately, this hybridization has been used by the unscrupulous to avoid listing the California Tiger Salamander on the endangered species list. See here and here. This latter link is interesting in the way it distorts scientific research. If you regularly read Chris Mooney it will sound all too familiar.
Anyway, I hope that helps.
