Though I'm a bit late on this conversation, I agree with BC. The adaptations and life styles of Dicampts & Ambystoma tigrinum are very different and in the wild I would doubt they would ever meet together. With Tiger Salamanders spend a lot of their life in quite warm ponds & lakes and Dicampts spendy their time mostly in or around cold fast flowing streams with little sediment. In captivity if you were to try to breed these one or the other would be at risk from the conditions in which the other needs to breed.
Now as for Lampropeltis & Pantherophis (Elaphe) guttata, these 2 genus are extremely closely related. The 3 U.S. genus (Pantherophis, Lampropeltis, & Pituophis) are closely related and have a much adaptations/behaviors/etc in common. These all often inhabit the same types of environments in the U.S. and are known to occasionally hybridize with one another. Though the offspring are usually "mules" (infertile), they have over many trials in captivity successfully had offspring which were fertile. Captive breedings were even able to accomplish a breeding which led to like a 50% Bull Snake x 25% Cali Kingsnake x 25% Corn Snake. There have been some other unusual hybrids in snakes (in captivity) which haven't proven fertile to my knowledge; Woma & Carpet Python, Ball x Jungle Carpet Python, & Carpet Python x Macklot's Python. Though snakes use chemosensory as well to detect mates, their courtship is pretty similar and I wouldn't be surprized if their pheromones weren't much different in subfamilies.
Note 1: Dealing with a good handful of Corn Snakes, I know that some individuals would court a hose if they thought they would get lucky.
TTFN,
Mark
http://www.flickr.com/photos/mark_leppin/