The Sonoran Desert is thought to have the greatest species diversity of any desert in North America, and that diversity occurs over relatively fine spatial scales. The Sonoran Desert is home to at least 60 species of mammals, more than 350 bird species, 20 amphibians, some 100 reptiles, and about 30 species of native fish. More than 2,000 species of plants have been identified in the Sonoran Desert, and each of the three physiological groupings of vascular plants (C3, C4, and CAM photosynthetic pathways) dominate one or more major biotic communities.