A taxonomic revision and phylogenetic study of the genus Chione dc. (Rubiaceae).

摘要

In the present study, I address the taxonomy and relationships (both intrageneric and intergeneric) of the genus Chione. Chione (family Rubiaceae) was established in 1830, but has never been the subject of taxonomic revision. This genus has traditionally been placed in the tribe Chiococceae, but this placement has recently come into question.; I here carry out a revision of the genus Chione, on the basis of morphology. I find two species, C. exserta and C. seminervis, to be morphologically divergent, especially in fruit structure, from the definition of Chione. I remove these species from the genus (now referred to as "Chione s.s.") and establish the new genus Colleteria for them. The character states that were previously employed to distinguish different species in Chione s.s.. appear to vary continuously among populations. I have not identified any new characters with which to distinguish species, and therefore consider Chione s.s. to contain only one species, Chione venosa. Morphological tendencies in certain populations do permit the description of four groups within C. venosa, which I recognize as varieties: C venosa var. buxifolia , var. cubensis, var. mexicana, and var. venosa.; I utilize nucleotide sequence data to reconstruct evolutionary relationships among Chione s.s., Colleteria, and other genera in the family (with nrITS, rps16, and trnL-F DNA regions), and among populations of Chione venosa (with the 5S-NTS region of DNA). Resultant phylogenetic hypotheses show strong support for Chione s.s. as a monophyletic unit, and for Colleteria as the sister group to Chione s.s. Results support the removal of Chione s.l. from the Chiococceae and indicate that Chione s.s. and Colleteria have closer relations to the genera Cosmibuena, Hamelia, and Hoffmannia. Although there are several alternative and conflicting phylogenies at the intrageneric level, I can conclude that Chione venosa var. buxifolia appears to be derived from C. venosa var. venosa.