it is an interesting question, and i have been racking my brain for an answer. clearly morelia have evolved to have different markings on the tail end (eg bredli with a lot of black, diamonds with brighter yellows), but i cannot fathom how this has been selected for...
whilst pondering this i came up with another question:
why do so many species have barred lips?
it must have some significance because you see it in such a variety of distantly related species.