Cannabis: an example of taxonomic neglect

Native apparently somewhere in central Asia, cannabis is at present one of the most widely disseminated cultivated plants. Cannabis as we know it has developed together with man as a multi-purpose economic plant; and, as a result of selection for desirable characteristics, it has become one of the most variable of cultivated plants. Due to the extraordinary plasticity and variability of cultivated cannabis, there can be no progress in unravelling the taxonomic complexities in the genus until the biology of the wild populations is investigated. The genus has been and still is widely considered to be monotypic, especially by botanists who have not studied the classification of the genus in depth: we believe this results from lack of taxonomic investigations of wild cannabis in its native habitat or even of comparative studies of the range of variation in cultivated hemp. A polytypic concept of the genus is not new: in 1783 Lamarck recognized Cannabis indica as "very distinct" from the species which Linnaeus had named Cannabis sativa. In 1924, Russian botanists, who studied wild populations of cannabis, recognized a third species, Cannabis ruderalis. Their work has not been widely accepted, partly due to conservative attitudes to changing established beliefs in the monotypic nature of the genus. Several British and American taxonomists who have investigated the genus now favor the polytypic concept. There may be significant chemical differences in content of cannabinolic and other constituents among the species. The paper reviews the taxonomic history of the genus and presents data in support of the polytypic concept. (Author' s abstract)