The distribution of Indica is wider and overlaps partly with tropical Japonica; in addition, it is assumed that the characteristic of cultivation of the Indica is closely related to the upland rice agriculture.
熱帯ジャポニカは、インディカの分布と重なりながら、更に広い範囲に分布し、陸稲と密接に結びついているのが特徴であるとされる。