Kupeantha (Coffeeae, Rubiaceae), a new genus from Cameroon and Equatorial Guinea.

Two new coffee relatives (tribe Coffeeae, Rubiaceae), discovered during botanical expeditions to Cameroon, are examined for generic placement, and the placement of three previously known species (Argocoffeopsis fosimondi, A. spathulata and Calycosiphonia pentamera) is reinvestigated using plastid sequence (accD-psa1, rpl16, trnL-F) and morphological data. Seed biochemistry of the new species and pollen micromorphology (only one of the two species) are also studied. Based on the plastid sequence data, the new taxa are nested in a well-supported monophyletic group that includes Argocoffeopsis and Calycosiphonia. Within this clade, three well-supported subclades are recovered that are morphologically easy to diagnose: (1) Calycosiphonia (excluding C. pentamera), (2) Argocoffeopsis (excluding A. fosimondi and A. spathulata), and (3) a clade including the above excluded species, in addition to the new species. Based on the results, Kupeantha, a new genus of five species, is described, including two new Critically Endangered taxa from the Highlands of Cameroon: Kupeantha ebo and K. kupensis. Phytochemical analysis of Kupeantha seeds reveals compounds assigned as hydroxycinnamic acid derivatives, amino acids and ent-kaurane diterpenoids; caffeine was not detected. Kupeantha is the first new genus described in tribe Coffeeae in 40 years.