The morphs sometimes just come from different imports of frogs from different places. They usually have the same care requirements but some can be bigger or smaller and thus, no morph should be mixed. Josh's Frogs has many dart morphs. A normal leucomelas i belive has both spots and stripes. The "fine spot" morph is smaller and has mostly spots. The "british guyana" morph has pretty much only stripes and is larger than a regular leuc. There are other examples but thats the only one i can think of. Its mostly through breeding out recessive traits in order to get the desired size, color, and pattern.