Phylogeny and classification of the coffee family (Rubiaceae, Gentianales): Overview and outlook

The use of molecular data in phylogenetic reconstruction during more than three decades has greatly improved our understanding of the macroevolutionary history of the coffee family (Rubiaceae) and has provided a solid basis for improvement of its classification. Based on the results of 130 studies, among them most recent phylogenomic works, we present a consensus phylogeny and a robust classification of Rubiaceae that shed light on the evolutionary success of this highly diverse angiosperm family and can serve as a framework for ecological and evolutionary studies. There are more than 14,000 species and about 580 accepted genera of Rubiaceae that are assigned to 71 tribes, of which 68 are classified in two subfamilies (Dialypetalanthoideae with 38 tribes and Rubioideae with 30 tribes). Three tribes (Acranthereae, Coptosapelteae, Luculieae) remain unclassified as to subfamily. Sixty-three of these 71 tribes are assigned to nine informal alliances (four in Rubioideae and five in Dialypetalanthoideae). These tribes are listed in alphabetical order within their respective alliances. Five tribes, one (Coussareeae) in Rubioideae and four (Airospermeae, Jackieae, Retiniphylleae, Steenisieae) in Dialypetalanthoideae, are excluded from these alliances due to unclear or conflicting phylogenetic positions. Thirty-six tribes retain their tribal status but receive new generic limits to remedy their previous para- or polyphyletic nature. Twenty-nine tribes not implemented in previous classifications have been added, of which three (Chioneae, Glionnetieae, Temnopterygeae) are newly described here. Basic information on phylogenies, distributions, former classifications, and useful references to previous works are provided for all accepted tribes, and future perspectives are discussed.