Experimental Endozoochory of <b><i>Cannabis sativa</i></b> Achenes

Abstract

The mechanism by which Cannabis sativa dispersed from its center of origin remains an open question. The literature provides many hypotheses, which we review for the first time, but experiments are few. Darwin was interested in zoochory – the transport of plants by animals. He demonstrated endozoochory (transport of seeds via animal digestive systems) of C. sativa achenes (seeds) by carrier pigeons, but he did not quantify achene survival rates. We assessed mammalian endozoochory in a triplicate experiment: feeding C. sativa achenes into a simulated gastrointestinal system, a dog, and a human. The in vitro system subjected achenes to sequential digestive enzymes. Achenes were planted in potting soil and monitored for emergence under growroom conditions. The in vivo experiments added achenes to a normal morning meal (dog food or granola). Feces were collected for daily instillation into an outdoor garden and monitored for seedling emergence for 16 days. Control achenes were planted directly into soil without ingestion. In the in vitro study, 34.7% of the digested achenes emerged as seedlings. The in vivo emergence rates were 10.3, 1.3, and 76.0% for the dog, human, and control conditions. The three groups differed significantly (χ² = 1,264.93, p < 0.0001). Achene survival was greatest under in vitro conditions, which lacked a mastication step, compared to dog (minimal chewing) and human (maximal chewing) conditions. Although C. sativa lacks evolutionary traits for classic endozoochory (i.e., a fleshy fruit), it seems well adapted to this manner of seed dispersal.

Beyond Scatter-Hoarding and Frugivory: European Corvids as Overlooked Vectors for a Broad Range of Plants

“…Most contemporary research on avian endozoochory is focussed on frugivores, and fruit has been reported to make up 10% or more of the diet of 83 species in the crow family (Corvidae) ( Table 5.1 in Wenny et al, 2016). Dispersal of seeds embedded in the fleshy pulp of an edible berry or fruit has been called "classic endozoochory" (McPartland and Naraine, 2018). This corresponds to the long-standing practice of assigning "dispersal syndromes" to plant species on the basis of diaspore morphology, in which only fleshy-fruited diaspores are assigned to a "endozoochory syndrome" (van der Pijl, 1982;Perez-Harguindeguy et al, 2013).…”

The morphology of Cannabis sativa L. Achenes

“…Very little is known about the seed dispersal of C. sativa, although it has been hypothesized that gravity, mammals, birds, insects, water and (of course) humans are significant vectors (Small, 2016). For example, the extent of survival through animal digestive systems is undocumented, to the best of my knowledge (McPartland & Naraine, 2018). It would be interesting to examine how survival and dispersal are related to the hull characteristics documented in the present thesis.…”