my guess is they were originally the exact same species, but due to separation, and time they slowly changed to meet their environment and became still the same but visibly distinctive. its kind of like comparing white tailed deer in florida to the ones in MN, the fla ones run around 100# or less, and the ones in MN can go well over 200, yet are the same animal. just my theory, and with that i have no problem crossing guppy's, and endlers.