Problem
Genetic data indicates that the California Tiger Salamander (Ambystoma californiense) was separated from the Barred Tiger Salamander (A. tigrinium) for over 5 million years. Sometime around 1950, humans introduced the A. tigrinium to the range of A. californiense. The two "species" will hybridize in the field. In some habitats, hybrids have lower fitness than pure A. californiense. In others, hybrids have greater fitness.
Based on your understanding of the Biological Species Concept, is A. californiense a valid species? Briefly explain your choice. Does it matter that humans caused the two lineages to come into contact? What additional information would you like to have to make your decision?