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. 2020 Apr 3:144:81-112.
doi: 10.3897/phytokeys.144.46700. eCollection 2020.

A classification of endangered high-THC cannabis (Cannabis sativa subsp. indica) domesticates and their wild relatives

John M McPartland  1   2 , Ernest Small  3
Affiliations

A classification of endangered high-THC cannabis (Cannabis sativa subsp. indica) domesticates and their wild relatives

John M McPartland et al. PhytoKeys. .

Abstract

Two kinds of drug-type Cannabis gained layman's terms in the 1980s. "Sativa" had origins in South Asia (India), with early historical dissemination to Southeast Asia, Africa, and the Americas. "Indica" had origins in Central Asia (Afghanistan, Pakistan, Turkestan). We have assigned unambiguous taxonomic names to these varieties, after examining morphological characters in 1100 herbarium specimens, and analyzing phytochemical and genetic data from the literature in a meta-analysis. "Sativa" and "Indica" are recognized as C. sativa subsp. indica var. indica and C. sativa subsp. indica var. afghanica, respectively. Their wild-growing relatives are C. sativa subsp. indica var. himalayensis (in South Asia), and C. sativa subsp. indica var. asperrima (in Central Asia). Natural selection initiated divergence, driven by climatic conditions in South and Central Asia. Subsequent domestication drove further phytochemical divergence. South and Central Asian domesticates can be distinguished by tetrahydrocannabinol and cannabidiol content (THC/CBD ratios, ≥7 or <7, respectively), terpenoid profiles (absence or presence of sesquiterpene alcohols), and a suite of morphological characters. The two domesticates have undergone widespread introgressive hybridization in the past 50 years. This has obliterated differences between hybridized "Sativa" and "Indica" currently available. "Strains" alleged to represent "Sativa" and "Indica" are usually based on THC/CBD ratios of plants with undocumented hybrid backgrounds (with so-called "Indicas" often delimited simply on possession of more CBD than "Sativas"). The classification presented here circumscribes and names four taxa of Cannabis that represent critically endangered reservoirs of germplasm from which modern cannabinoid strains originated, and which are in urgent need of conservation.

Keywords: Cannabinoids; Cannabis sativa; classification; ecology; germplasm; marijuana; nomenclature.

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Figures

Figure 1.
Figure 1.
Line drawing adapted from Anderson (1980), courtesy of the Harvard University Herbaria and Botany Libraries.
Figure 2.
Figure 2.
Shifts in THC/CBD ratios over time; data from 47 numbered studies in Suppl. material 1: SF.9. Central Asian landraces in unitalicized red (n =13 studies); “Indica” in underlined unitalicized red (n= 9); South Asian landraces in italicized green (n =18 studies); “Sativa” in underlined italicized green (n =7 studies). Size of numeral reflects the number of accessions analyzed in that study.
Figure 3.
Figure 3.
Representative achenes of four varieties Aindica, Rajshahi (Bangladesh), Clarke 1877 (BM) Bindica, Coimbatore (India), Bircher 1893 (K) Cindica, South Africa, Hillig 1996; (IND) Dhimalayensis neotype Ehimalayensis, Bareilly (India), Roxburgh 1796 (K). Fhimalayensis, East Bengal (Bangladesh) Griffith 1835 (GH) Gafghanica neotype Hafghanica epitype Iafghanica Yarkant (Xīnjiāng), Henderson 1871 (LE) Jasperrima lectotype Kasperrima Nuristān (Afghanistan), Street 1965 (F) L Kailiyskiy Alatau (Kazakhstan), Semenov-Tyan-Shansky 1857 (LE).
Figure 4.
Figure 4.
Two varieties of C. sativa subsp. indica from South Asia. On left a var. indica. On right b var. himalayensis.
Figure 5.
Figure 5.
Type specimens of C. sativa subsp. indica var. afghanica. Neotype on left (a), epitype on right (b).
Figure 6.
Figure 6.
Type specimens of C. sativa subsp. indica var. asperrima. Lectotype on left (a), epitype on right (b).
Figure 7.
Figure 7.
Distribution of herbarium specimens. Red circles: var. asperrima; green triangles: var. himalayensis. Floristic zones based on Djamali et al. (2012): Red area: Irano-Turanian region; green area: Indian region; lilac area: Saharo-Sindian region. Other floristic regions not demarcated and unlabeled. Background base map by Natural Earth, free open-source map data (https:// www.naturalearthdata.com).
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