About 175 species: most in the tropics and subtropics of America, ca. 70 species in Africa, widely introduced elsewhere; three species (introduced) in China.

• 大约175种：多数生于美洲的热带和亚热带，约70种分布于非洲，在别处广泛引进栽培；中国有3种(均为引入栽培)。