The number of species in the coffee genus has increased from 104 to 124 as a result of a new systematic study.
The generic delimitation Coffea has troubled coffee researchers and taxonomists for more than 250 years. Only recently has molecular systematic research shown that, of the many genera previously associated with Coffea, only one genus, Psilanthus (20 species), is in fact closely related.
Indeed, some species of Psilanthus have previously been included in Coffea (Davis, 2010), as well as being used as local coffee substitutes and in trials for coffee production. Biological evidence from a variety of other sources also points to a close association between Coffea and Psilanthus, and it has been suggested on a number of occasions that they should be united into a single genus.
Davis, A. P. (2010). Six species of Psilanthus transferred to Coffea (Coffeeae, Rubiaceae). Phytotaxa 10: 41–45.
Davis, A. P., Tosh, J., Ruch, N. & Fay, M. F. (2011). Growing coffee: Psilanthus (Rubiaceae) subsumed on the basis of molecular and morphological data; implications for the size, morphology, distribution and evolutionary history of Coffea. Botanical Journal of the Linnean Society 167: 357–377.
Davis, A. P. (2011). Psilanthus mannii, the type species of Psilanthus, transferred to Coffea. Nordic Journal of Botany 29: 471–472.
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