Three main groups of populations were recognized by means of numerical taxonomic analyses: White Mountains of California (one population), Intermontane (Colorado Plateau and western Great Basin), and southwestern (remaining four populations).
L'analyse numérique fait ressortir trois groupes majeurs : celui des White Mountains de Californie (une population), celui de l'Intermontane (populations du Plateau du Colorado et de l'ouest du Grand Bassin) et celui du sud-ouest (les quatre dernières populations).