With its wide mouth charmingly outlined in yellow, the California tiger salamander always looks like it's smiling. But this beautiful amphibian is a discriminating species that can only thrive in ...

However, where the circle closes -- in the black zone on the map in Southern California -- the salamanders no longer interbreed successfully. The variation within a single species has produced ...

With its wide mouth charmingly outlined in yellow, the California tiger salamander always looks like it's smiling. But this beautiful amphibian is a discriminating species that can only thrive in ...