Black rats and Emoryi are not the same species, and probably do not breed with each other much in the wild. Several of the crosses you mentioned are just natural intergrades, splendida and speckled kings are the same species, as are bull and gopher snakes. The different milksnakes are also the same species. Corn and Red Rat Snakes are one and the same, just different common names. Wild rattlesnake hybrids have been found, but from all I have heard, they are very rare. Hybrid corn snake/Yellow Rat Snake Hybrids have supposedly been found in Florida, but most of those that I have seen have either looked like a yellow rat that retained its juvenile blotches, or a corn snake with faint dark striping, both of which are normal occurances in the pure form of either species. I've only seen one corn/yellow rat hybrid that looked like the real deal, and that one was captive produced.
>A interesting subject came up of Black Rats and Emoryi in Kansas >and maybe even of Missouri. While integration of milk snake are >oblivious in mostly Kansas and a small part believed in Missouri, >and of over 30 years of observing these species, I haven't known >or heard of integration of the 2 rat snakes in the wild where >distribution range clearly overlaps. I know or heard besides the >milk snake inter-breeding of Texas Rats, several species of >rattlesnakes, corn/red rat snakes, speckled king with splendida, >and even the Bull Snake and Gopher Snake of west Texas. What do >you think ???????