Now thats the million dollar question! There are several ways to look at the barbatum group. Two popular ways are; its one species with a massive land coverage where some look like the type barbatum and others are callosum sublaeve at their extreme or they started out as two separate species, barbatum and callosum expanded their area of occupation and have inter-bred so much so its hard to tell apart with many intermediates. I favor the two species growing into each other myself.