A strange duck sent in a link to this story about hybridization between a native and introduced salamander in California. The interaction between the California tiger salamander (Ambystoma californiense) and Eastern tiger salamander (Ambystoma tigrinum) is not news in itself (the ISW pointed to research on the subject back in 2003) - Eastern tiger salamanders established in California following the use of their larvae as bait for the past several decades. But now new evidence indicates that the hybrid offspring exhibit what is known as "hybrid vigor" - they are more fit than either parent species.
That certainly doesn't bode well for the endangered California species, whose populations were already on the decline. The researchers are concerned that the greater fitness of the hybrids could lead to the eventual loss of the California species, as over time crossing of hybrids with parent species (and other hybrids) leads to permanent integration of non-native genes into all tiger salamanders in the region.
The NSF does a nice job with their writeup of this study but somehow fails to have more than a passing reference to the actual peer-reviewed article in PNAS. Here's a link to the abstract.