Complex sentence: It is native to western North America, where it occurs in the mountains straddling the border between British Columbia and Alberta and Montana, with isolated populations occurring as far north as Yukon and as far south as Colorado.
Split into simpler sentences: It is native to western North America, where it occurs in the mountains straddling the border between British Columbia and Alberta and Montana. It has a disjunct distribution, with separate populations occurring as far north as Yukon and as far south as Colorado.