Genghis Kush.
Well-known member
Latitudinal Adaptation and Genetic Insights Into the Origins of Cannabis sativa L - PMC
Cannabis is one of the most important industrial crops distributed worldwide. However, the phylogeographic structure and domestication knowledge of this crop remains poorly understood. In this study, sequence variations of five chloroplast DNA ...
pmc.ncbi.nlm.nih.gov
Latitudinal Adaptation and Genetic Insights Into the Origins of Cannabis sativa L.
One major finding of this study is that Cannabis can be divided into three distinct genetic lineages (Figure 1), namely the H, M, and L haplogroups. Interestingly the haplogroups exhibited latitudinal gradients distribution and this distinctive high-middle-low latitude pattern was supported by NETWORK, AMOVA, SAMOVA, and Mantel Tests based on cpDNA data. High-latitude group members (group H) were mainly distributed in regions north of about 40° N and Low-latitude group members (group L) were mainly distributed in areas south of about 30° N, while the middle-latitude group members (group M) were mainly distributed in the zone between about 30° N and 40° N. This current distribution pattern implies an adaptation to distinct latitudinal gradient climatic features. In the present study, the lineage distribution was significantly correlated with latitude and climatic factors. In particular, the day-length has a strong and significant (r2 = 0.6024, p < 0.001) influence on the haplogroup distribution frequencies in each population by RDA analysis and ANOVA partition (Table 3). Furthermore, our field phenotype trial results showed that phenological and morphological traits had a negative, very strong, and significant correlation with latitude of accession origin. For instance, Group H is characterized by short plant height, thin stem, fewer branches, and short life cycle. On the contrary, Group L demonstrates opposite characteristics compared with Group H. This is well-linked to the quantitative (facultative) short-day plant trait of Cannabis. The flowering of Cannabis is normally induced by a required duration of days with a minimum uninterrupted period of darkness (10–12 h for most cultivars) (Small, 2015). Due to the sensitivity to photoperiod, shortening day length can promote Cannabis plant pre-flowering. On the contrary, prolonged day length would delay this crop from shifting from a vegetative stage into a reproductive stage. Indeed, the northernmost distribution of group L is located at about 43° N, which is consistent with previous observations that cultivars from the southern (low latitude) areas have extended vegetative cycles and failed to produce seeds when grown in the North (High latitude areas) (Pahkala et al., 2008; Amaducci et al., 2012; Small, 2015). Our results suggest that photoperiod sensitivity is a potential factor that prevents group L from extending further north. In contrast, the southernmost boundary of group H is 31° N (landrace C224 in Figure 1A). It was surprising to observe that Cannabis lineages still present a distinctive high-middle-low latitude distribution pattern after several thousand years despite human activities. Nevertheless, each of the three haplogroups is not strictly limited to its main corresponding geographical locations: North of 40° N (Haplogroup H), 30 to 40° N (Haplogroup H), and South of 30° N (Haplogroup L). Some haplotypes of the haplogroups were aberrantly growing out of the main distribution latitude range (Figure 1A). For instance, haplotype H3 in cultivar C224, which belongs to Haplogroup H, was found in lower latitude areas around 31° N; while the haplotype H5 in wild population XH and ZL, which belongs to Haplogroup L, was found at a higher latitude area around 43° N. These exceptions may result from the influences of human agricultural activities. Clarke and Merlin (2016) have stated, “Humans and the Cannabis plant share an intimate history spanning millennia.” There might have been much more stringent distribution limits between haplogroups prior to human activities (see below).
Multiregional Domestication Origin of Cannabis Plant
Each of the three haplogroups (M, L, and H) identified in this study contains haplotypes from both wild populations and cultivars. Within each haplogroup, the wild and domesticated populations shared the most common haplotypes. For instance, haplotype H1, H3, and H4 are the most common haplotypes shared by the wild and domesticated populations in Group H; similar trends are observed for haplotype H9 in Group M, and haplotypes H5 and H10 in the Group L. The fact that the haplotype of the domesticated Cannabis cultivars are not limited to one of the three haplogroups indicates that there are probably multiregional domestication origins for this crop from the three subspecies of Cannabis. Otherwise, the same genotype (haplogroup) should have been detected in different cultivars from high-middle-low latitude regions if the cultivars were domesticated from one single region. AMOVA analyses results also demonstrate that there is no significant difference (Fst = 0.023) between the wild population group and domesticated cultivar group based on cpDNA data. This molecular evidence is in accordance with the multiregional origin of human use of the cannabis plant proposed based on archaeological investigation (Long et al., 2016) and Fossil pollen studies (Mcpartland et al., 2018). Actually, contemporaneous cannabis achenes (5,000–10,200 years ago) have been found in more than ten different archaeological sites located in the two distal parts (both Europe and East Asia) of the continent (Long et al., 2016). Thus the domestication of C. sativa could have occurred in more than three areas in Eurasia.These accumulating pieces of evidence also hint that a rank below that of species is more reasonable. Thus we suggest that Cannabis should be considered as a monotypic genus with only one species, Cannabis sativa L. Considering that the three distinctive lineages revealed by cpDNA molecular markers also clearly demonstrated obvious geographic regions as stated above, this species can be further divided into three subspecies. Meanwhile, based on nomenclature history of this species, original geographic range, and basic difference in phenotype, we recommend the naming of the three subspecies as: Cannabis sativa subsp. sativa, C. sativa subsp. indica, and C. sativa subsp. ruderalis, corresponding to the Haplogroup M, Haplogroup L, and Haplogroup H, respectively. Small and Cronquist (1976) also pointed out that C. sativa subsp. sativa is typically distributed at areas with latitudes north of 30° N. Our present results that the haplogroup M (i.e., subsp. sativa) is distributed in areas ranging from 27 to 43° N, is largely consistent with the observations by Small and Cronquist.
The Central-Asia-Origin has been the prevalent opinion for C. saltiva (de Candolle, 1885; McPartland, 2018), although some botanists considered Europe as the center of origin (Thiébaut de Berneaud, 1835; Keppen, 1886), or a region spanning Asia and Europe (Herder, 1892; Vavilov, 1926). However, our molecular analyses revealed for the first time that the low latitude region distributed subsp. indica (Haplogroup L) possesses the basal group position within Cannabis, indicating that this species is possibly originated from low latitude areas in the evolutionary history of this plant. This finding does not support the hypothesis of the Central-Asia-origin of Cannabis, but is partly in agreement with the speculation of Linnaeus (1737) that the native range of C. saltiva was India Orientali (encompassing the Indian subcontinent, southeastern Asia, and the Malay Archipelago), Japonia (Japan), and Malabaria (the Malabar coast of southwest India). Indeed, the seeds from wild Cannabis populations in India are remarkably small, unlike those collected from any other area, also indicating that the wild Indian populations may be an ancient wild form (Small, 2015).
Last edited:
