quality:corruption
Species

The number of species recognised within this genus varies sharply, from 16 to 25 or more according to the authority followed, because most populations are small and isolated, and whether they should be accorded specific, subspecific or varietal rank is difficult to ascertain. Current tendencies are to reduce the number of recognised species; when a narrow species concept is adopted, the varieties indented in the list below may also be accepted as distinct species. See also the New World species (below) for a likely split in the genus in the future.