The U.S. is one of 17 megadiverse countries containing a large amount of endemic species: about 17,000 species of vascular plants occur in the contiguous United States and Alaska, and more than 1,800 species of flowering plants are found in Hawaii, few of which occur on the mainland. The United States is home to 428 mammal species, 784 bird species, 311 reptile species, and 295 amphibian species, as well as about 91,000 insect species.