Domesticated plants provide critical resources for food, fiber, and energy, but they can also be a source of weeds and invasive species when they escape and de-domesticate. Cannabis sativa L. is a fascinating case of a highly domesticated species with a known crop-to-weed history. However, in general, Cannabis has not been subjected to modern intensive agriculture due to prohibition of the species. With growing liberalisation of policy surrounding Cannabis, there is renewed interest and effort in intensive breeding and planting of the species. In conjunction, there are growing concerns regarding invasion risk of Cannabis as the species becomes more widely propagated and distributed, which may increase opportunities for escape. To understand potential invasion risks, we synthesized knowledge of Cannabis across the domestication-invasion cycle, which we provide as a framework to explain the process of how a domesticated crop transitions from cultivation to ferality to ultimately becoming invasive. We then outline research priorities for management solutions that minimize escape.
Results/Conclusions
The long history of Cannabis domestication and movement has resulted in extreme selected genetic divergence. There are considerable differences among cultivated and feral biotypes that may allow Cannabis to colonize a wide range of geographical regions. It is a synanthropic species that thrives in areas modified by humans, including disturbed soil that is high in nutrients such as roadsides, ditches, and abandoned fields. Cannabis is known to have naturalised (i.e., maintain self-sustaining populations outside of cultivation) in 35 countries across five continents. It has been formally described as a ‘weed’ (i.e., problematic or undesired plant) in 29 countries across four continents. Despite a known history of ferality, and as a weed, much of the ecology of the species is based on observational notes among a few scattered studies. We identified three priority areas where research is needed to better understand how Cannabis transitions through the domestication-invasion cycle: (1) establishment- identification of scenarios where risk of escape are highest and persistence of the plant outside of cultivation, (2) phenotypic variation – differences in invasiveness across biotypes, and (3) impacts – the ecological effects of escaped and feral Cannabis on native species and ecosystems.