the transition zone region (diagonal across Arizona–NW-to-E-central); Colorado Plateau to northeast, lower level deserts of Basin and Range to west-(NW), SW, and south
by the Hoover Dam/Lake Mead, (w&nw)(Mojave Desert) Chihuahuan Desert by extreme SE Arizona All of central, and sw Arizona-lower elevations below Mogollon Rim: part of Sonoran Desert; even the bottom of the Grand Canyon(a lower elevation) would have Sonoran Desert biota/Sonoran influence