| 1. Appalachian |
| 2. California |
| 3. Desert |
| 4. Eastern Tallgrass Prairie and Big Rivers |
| 5. Great Basin |
| 6. Great Northern |
| 7. Great Plains |
| 8. Gulf Coast Prairie |
| 9. Gulf Coastal Plains and Ozarks |
| 10. North Atlantic |
| 11. North Pacific |
| 12. Peninsular Florida |
| 13. Plains and Prairie Potholes |
| 14. South Atlantic |
| 15. Southern Rockies |
| 16. Upper Midwest and Great Lakes |
| 17. Aleutian and Bering Sea Islands |
| 18. Arctic |
| 19. Northwest Boreal |
| 20. Western Alaska |
| 21. Pacific Islands |
| 22. Caribbean |