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Title: Phylogeography of the wild and cultivated stimulant plant qat (Catha edulis, Celastraceae) in areas of historic cultivation1

Author
item TEMBROCK, LUKE - Colorado State University
item SIMMONS, MARK - Colorado State University
item Richards, Christopher
item Reeves, Patrick
item Reilley, Ann
item CURTO, MANUEL - The University Of Porto
item MEIMBERG, HARALD - University Of Natural Resources & Applied Life Sciences - Austria
item NGUGI, GRACE - National Museums Of Kenya
item DEMISSEW, SEBSEBE - Addis Ababa University
item WALI AL KHULAIDI, ABDUL - King Abdulaziz University
item MANSOOR, AL-THOBHANI - Sana'A University
item Simpson, Sheron
item VARISCO, DANIEL - Qatar University

Submitted to: American Journal of Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/2/2017
Publication Date: 4/1/2017
Citation: Tembrock, L., Simmons, M., Richards, C.M., Reeves, P.A., Reilley, A.A., Curto, M.A., Meimberg, H., Ngugi, G., Demissew, S., Wali Al Khulaidi, A., Mansoor, A., Simpson, S.A., Varisco, D. 2017. Phylogeography of the wild and cultivated stimulant plant qat (Catha edulis, Celastraceae) in areas of historic cultivation1. American Journal of Botany. 104: 538-549.

Interpretive Summary: Qat (Catha edulis, Celastraceae) is a woody plant species cultivated for its stimulant alkaloids. Qat is important to the economy and culture in large regions of Ethiopia, Kenya, and Yemen. Despite the importance of this species, the wild origins and dispersal of cultivars is unknown. We sampled 1561 wild and cultivated individuals across the historic regions of its wild range and cultivation. We inferred the genetic diversity and relationships among these samples using a set of 17 DNA markers (simple sequence repeats). We were able to reconstruct the sources of the cultivated samples and identified the center of its earliest cultivation from the wild. We consider this species is in the earliest stages of domestication and the data underscores features of genetic divergence common in many domesticated tree species.

Technical Abstract: Qat (Catha edulis, Celastraceae) is a woody plant species cultivated for its stimulant alkaloids. Qat is important to the economy and culture in large regions of Ethiopia, Kenya, and Yemen. Despite the importance of this species, the wild origins and dispersal of cultivars have only been described in often contradictory historical documents. We examined the wild origins, human-mediated dispersal, and genetic divergence of cultivated qat relative to wild qat. We sampled 17 SSR markers and 1561 wild and cultivated individuals across the historic areas of qat cultivation. Based on genetic structure inferred using Bayesian and non-parametric methods, two centers of origin in Kenya and one in Ethiopia were found for cultivated qat. The centers of origin in Ethiopia and northeast of Mt. Kenya are the primary sources of cultivated qat genotypes. Qat cultivated in Yemen is derived from Ethiopian genotypes rather than Yemeni wild populations. Cultivated qat with a wild Kenyan origin has not spread to Ethiopia or Yemen whereas a small minority of qat cultivated in Kenya originated in Ethiopia. Hybrid genotypes with both Ethiopian and Kenyan parentage are present in northern Kenya. Ethiopian cultivars have diverged from their wild relatives, whereas Kenyan qat has diverged less. This pattern of divergence could be caused by the extinction of the wild-source qat populations in Ethiopia due to deforestation, undersampling, and/or artificial selection for agronomically important traits.