| Southwest Basins and Ranges | Level 3 (Parent) |
|          Northwest Arizona Ranges | Level 4 (Sibling) |
|          North Sonoran Desert Ranges | Level 4 |
|                  Kofa Area | Level 5 (Child) |
|                  Harquahala Area | Level 5 (Child) |
|                  Cabeza Prieta Area | Level 5 (Child) |
|                  Organ Pipe Area | Level 5 (Child) |
|                  Maricopa Area | Level 5 (Child) |
|                  South Phoenix Area | Level 5 (Child) |
|                  Baboquivari Area | Level 5 (Child) |
|                  La Lesna Area | Level 5 (Child) |
|                  San Luis Area | Level 5 (Child) |
|                  West Tucson-Nogales Area | Level 5 (Child) |
|          South Sonoran Desert Ranges | Level 4 (Sibling) |
|          Southeast Arizona Ranges | Level 4 (Sibling) |
|          Southwest New Mexico Ranges | Level 4 (Sibling) |
|          Southeast New Mexico Ranges | Level 4 (Sibling) |
|          Trans-Pecos Texas Ranges | Level 4 (Sibling) |