Mesquite is a common name for several plants in the genus Prosopis, which contains over 40 species of small leguminous trees. They are native to the southwestern United States and Mexico (except the creeping mesquite, which is native to Argentina, but invasive in southern California). The mesquite originates in the Tamaulipan mezquital ecoregion, in the deserts and xeric shrublands biome, located in the southern United States and northeastern Mexico. It has extremely long roots in order to seek water from very far underground. The region covers an area of 141,500 km2 (54,600 sq mi), encompassing a portion of the Gulf Coastal Plain in southern Texas, northern Tamaulipas, northeastern Coahuila, and part of Nuevo León. As a legume, mesquite is one of the few sources of fixed nitrogen in the desert habitat.