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Coffee (Rubiaceae) Phylogeny

Coffea arabica L. in Cameroon © Martin Cheek

The genus Coffea (Rubiaceae) comprises c. 100 species and contains the two main species used in the production of the beverage coffee: C. arabica and C. canephora. The objectives of this project are to: 1) produce a family tree (phylogeny) for coffee and its relatives based primarily on DNA sequence data; 2) use the DNA data to investigate the circumscription of species and the relationships between them; 3) use the family tree (phylogeny) to investigate the biogeography of coffee, and assess the historical relationships between Africa, Madagascar, the Mascarene Islands, Asia and Australasia; 4) provide training in molecular systematics for individuals and institutes in Africa and the Mascarenes; 5) integrate DNA phylogeny data with other fundamental biodiversity information on coffee species and make it widely accessible.

So far c. 75% of all Coffea species have been sequenced with five DNA regions (plastid: trnL intron, trnL-F IGS, rpl16 and accD-psa1; nuclear: ITS). Other plastid regions likely to provide systematic data are being investigated. The resulting phylogenetic trees show that Coffea can be divided into three main groups, which are more or less congruent with three regions: West Africa, East Africa and Madagscar-Mascarenes. The work has helped to gain further understanding of the origin of C. arabica, and in particular the origin of its parentage. The circumscription of several new species has been supported by our new sequence data. The phylogeny also allows hypotheses to be made about the morphological evolution within Coffea, particularly in Madagascar.

In a broader study using sequence data using chloroplast DNA (trnL intron, trnL-F IGS, rpl16 and accD-psa1), we have been able to identify the genera that have a close phylogenetic relationship with Coffea (tribe Coffeeae). The closest relative of Coffea is undoubtedly the genus Psilanthus; nine other genera are proposed as close relatives (all members of the Coffeeae).

The results of the Coffee Phylogeny project are being divided into four separate papers, of which the first was submitted in 2005.

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