1.9.3 Classification Difficulties Due to Obliteration
of Populations by Humans
People often distribute crops to foreign areas, providing opportunities for genetic
exchange with related species, and creating habitats (frequently weedy) where
hybrids will survive. On occasion, the result is the extermination of the genetic
differences between once distinct groups and their natural distribution ranges. For
example, this has happened to alfalfa, a complex species derived historically from
two very different wild parents,Medicago sativaL. andM. falcataL. Over the last
six millennia, both in cultivation and in nature, these parental lineages have
hybridized so extensively that most plants everywhere are of hybrid origin, one can
no longer identify the overwhelming majority of plants as belonging to either
original species, and so it is preferable to reduce the original rank of the parents to
subspecies of one species (Small 2011 ). Cultivated assemblages are especially
prone to losing their distinctness or simply becoming extinct (Jeffrey 1968 ), as their
human masters’needs and tastes change. InCannabis, hybridization between the
most distinctive variations has largely obliterated populational differences, espe-
cially between the two groups offiber biotypes and between the two groups of
marijuana biotypes. The two kinds offiber plant (discussed earlier as groups 1 and
2) that have been recognized have been widely hybridized, by legal breeders,
because of the resulting hybrid vigor; and the two kinds of marijuana plant that
have been recognized (discussed earlier as groups 3 and 4) have also been widely
hybridized (mostly illicitly) to provide for the different psychological states that
many have come to appreciate, and also to generate plants with desired photope-
riodic and size characteristics to meet local needs. Indeed, according to Clarke and
Merlin ( 2013 ),“hybrids have become the predominant form of drugCannabis
grown throughout Europe and the New World.”Taxonomy is a practical activity,
and when most individuals encountered are hybrids, this needs to be considered for
classification purposes.
1.10 Classification of Domesticated Plants
with Special Reference toCannabis
1.10.1 Defining“Domestication”
In common language,“domestication”often refers to taming of wild animals, i.e.
habituating them to humans so that they are relatively manageable. In biology,
domestication is the process of choosing individuals of a species that have char-
acteristics making them useful to people, the selection usually occurring over
generations, so that the desired traits become geneticallyfixed. Almost all important
species currently employed in agriculture or for other human purposes are
domesticated. Although the phrase“cultivated plant”is widespread and is often
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