Cannabaceae family: a comparison between Cannabis, Humulus & Vitis
Cannabis history began long before humans. During it’s evolutionary pattern the plant adapted both to human desire and climate changes in an effort to colonise as much land as possible.
Wild forms of Cannabis, Humulus and Vitis have little resembling what we see today in commercial productions, due mainly, human influences.
Cannabis belongs to the Cannabaceae family, which is a small plant family made up of two important genera, Cannabis and Humulus.
Cannabis (or hemp as is called for industrial production mainly), is a superfamily comprising of two species: (Cannabis Sativa and C. Indica) and one putative species (C. Ruderalis), and Humulus (or hop as is commonly known) which include three species, H.Lupulus, H. Scandens, and H. Yunnanensis.
Differences and similarities
We can find many differences between Cannabis and Humulus such as growth habit (erect vs.
vining), leaf form (hand-shaped vs. webbed or heart-shaped), female inflorescence form (compact
elongated raceme flower cluster vs. cone-shaped strobilus) and divergent secondary metabolite
chemistry (oxigen-containing aromatic cannabinoids vs. bitter alpha-acids).
The two genera share many anatomical characteristics:
all cannabinaceae species are heliotropic, dioecious and anemophilous. This means that Cannabis and Humulus favour open sunny habitats where wind pollination is facilitated and that both give rise to female and male plants.
Cannabis likely evolved its upright growth habit, extensive branching and reduced foliage most likely
in mixed open woodland and woodlands steppe vegetation zones.
Humulus vines also required wind pollination, and in order to achieve exposure to it, vining up neighbouring vegetation was necessary so it likely evolved along sunny exposed woodland fringes, in distributed areas and along waterways, in exactly the same sort of open niche favoured by self-sown Cannabis today. (1)
In 1772, similarities between Humulus and Cannabis prompted an Italian botanist (Giovanni Antonio Scopoli), to consider the common hop a type of Cannabis, renaming it Cannabis Lupus, which was changed and rejected by taxonomists of later years. (2)
Despite not belonging to the Cannabaceae Family, Vitis (grapewine) is a Vitaceae member: similarly to Cannabis and Humulus, truly wild grapevines are dioecious and wind-pollinated with bird-mediated dispersal, whilst domesticated grapevines are today self-pollinating hermaphrodites.
Evolution of the Cannabaceae (cannabis & humulus) plants
Humulus employs hooked trichomes to attach to substrate as it climbs using its paired stipules at the base of each leaf petiole to create opposing tension between stem and climbed surface, further securing the vine to its support. (3)
We can see this as a highly specialised adaptation: since both Cannabis and Humulus likely evolved in sunny open environments, erect habit probably appeared first, and vining evolved as a later adaptation to a more specialised niche – woodland fringe.
Possibly vining (or Humulus itself) evolved as a result of competition with Cannabis, a closely related and aggressive coloniser of their mutually favourable habitat.
Where humans influences started?
Humulus, Cannabis and Vitis share long interactions with humans thanks to their economical,therapeutic and recreational qualities.
Most of the Humulus cultivated today is destined to the beer industry where only female H. Lupulus
inflorescences grown seedless in the absence of male pollinators are commercially useful as a
battering agent and preservative in beer. (3)
H. Lupulus cultivars are limited in their morphological variation in comparison with Cannabis cultivars and have a narrower genetic base. This is the result of historically early asexual propagation of only a few phenotypes favoured for medicinal value and eventually brewing.
Cultivated hop followed an evolutionary path characterised by initial rapid genome expansion via seed followed by asexual clonal reproduction of favourable phenotypes by hop breeders.
On the other hand, Cannabis has been traditionally propagated from seeds. Only in the late twentieth century with the introduction of indoor Cannabis production and the request for standardised strains by the therapeutic market, asexual reproduction took place. (4)
Evolution of Vitis
To even better understand the possible future evolution pattern of Cannabis it is useful to review the biological evolution and domestication also of the common grapevine (Vitis Vinifera) since this is much further down the vegetative domestication path of both Humulus and Cannabis.
In the case of grape, domestication brought many changes such as greater fruit yield and sugar
Selection for higher yield, more sugar content, and determinant maturation resulted also in changes in berry colour and size, as well as a crucial change from dioecious to hermaphrodite sexuality. (5, 6)
The sex pattern found in the cultivated hemp resembles to a certain extend the pattern found in Vitis.
The wild Cannabis is dioecious, (f/m) but from the point of view of fiber production, the average male plants are undesirable, because they die off shortly after flowering, much earlier than the females.
Therefore human selection has attempted to produce hemp fiber varieties which are either monoecious (or hermaphroditic), or varieties where both sexes mature at the same time. (7)
It’s important to understand that Cannabis’ gene pool may become further narrowed by gradual culling through human selection of economically unfavourable clonal lines and there are many potential long-term drawbacks associated to this practice.
When Cannabis gene pool reaches a genetic bottleneck caused by the preponderance of asexual reproduction, genetic diversity will decrease and susceptibly to pests and diseases will increase.
Vitis has long been propagated vegetatively, but the adoption of vegetative propagation (by cutting), is a double-edge sword.
Although providing benefits ensuring true breeding cultivars, it discourages the generation of unique cultivars through crosses. (8)
Wine and table grapes currently receive intense chemical applications to combat severe
pathogen pressures and the long term sustainability of the grape and wine industries will rely on
the exploitation of the grape’s tremendous natural genetic diversity to develop improved disease-
resistant grape cultivars.
Unfortunately, today the truly wild form of grape, V. Vinifera sup. Silvestris, is relatively rare.
Unlike some other domesticated plants, Cannabis is believed still to occur in wild populations in certain parts of Asia
and to exhibit in these populations an appreciable amount of inherent natural variability.
Under the pressures of selection, Cannabis also began to reveal characters and combinations of characters not found in wild or presumed wild populations. (9)
This phenomenon, started as an induced selection for higher production of THC, (driven from the interest of the recreational market), has now taken the lead on selection of few well evaluated chemotypes that allow for production of licensed standardised medical therapies.
Thus, alongside Cannabis selection for medical applications, agriculture practice should maintain stably cross overs and genetic variance, in order to avoid the problematics that evolved similarly with other domesticated species.
Environment, human desire and economic forces will continue to drastically shape these plants in the future.
Better understanding of Vitis and Humulus, give us great insight about the possible future evolutionary path of Cannabis and how to drive future manipulation in a long-sighted manner that may benefit both market demands and ecological sustainability.
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(1) Clarke, R. C., Merlin, M. D. (2014). Cannabis evolution and ethnobotany. Berkeley, California:University of California Press, pag. 353
(2) Giovanni Antonio Scopoli, Flora Carniolica, Vienna 1772, vol II pag 263
(3) Isnard S., and W. K. Silk (2009). “Moving with Climbing Plants from Charles Darwin’s Time into the
21st century”. American journal of botany 96 (7). 1205-21
(4) Clarke, R. C., Merlin, M. D. (2014). Cannabis evolution and ethnobotany. Berkeley, California:
University of California Press, pag. 354-355
(5) Grassi, F., F. De Mattia, G. Zecca, F. Sala, L. Massimo. 2008. “Historical Isolation and Range of
Expansion of Wild Grape”. Biological Journal of the Linnean Society 95 (3): 611-19
(6) Myles, S., A. R. Boyko, C. L. Owens, P. J. Brown, F. Grassi, R. K. Aradhya, B. Prins, A. Reynolds,
J. Chia, D. Ware, C. D. Bustamante, E. S. Buckler. 2011. “Genetic Structure and Domestication
History of the Grape”. PNSA 108 (9): 3530-35
(7) M. Demerec, (1958), Advances in Genetics, 9:pag. 239Academic Press Inc
(8) Myles, S., A. R. Boyko, C. L. Owens, P. J. Brown, F. Grassi, R. K. Aradhya, B. Prins, A. Reynolds, J. Chia, D. Ware, C. D. Bustamante, E. S. Buckler. 2011. “Genetic Structure and Domestication History of the Grape”. PNSA 108 (9): 3530-35
(9) Richard Evans Schultes, William M. Klein, Timothy Plowman and Tom E. Lockwood.(1974) Cannabis: an example of taxonomic neglect Botanical Museum Leaflets, Harvard University. 23:(9) pp. 338