Mosiera is a New World genus of approximately 12 species of trees and shrubs that occur primarily in tropical dry, deciduous or partially deciduous forests, mainly in the Caribbean. Two species occur in eastern and southern Mexico, one of these also occurring in Guatemala, and only one species occurs in South America (Brazil). Ecologically, Mosiera appears to be restricted to gypsum, limestone or serpentine soils. Only one species, M. longipes, is widely distributed throughout the Caribbean, the other species are generally narrowly endemic. The center of diversity of the genus is in eastern Cuba which corresponds to the center of botanical diversity of the Antilles as a whole. Described by Small in 1933, the boundaries of Mosiera have never been adequately defined until recently. Mosiera has a combination of characters which cause it to be superficially similar to other genera (i.e., Anamomis or Eugenia of the subtribe Eugeniinae or Myrtus or Psidium in the subtribe Myrtinae). The genus was first comprehensively described in 1992 by Landrum, however, to date only three species have been systematically treated and no objective phylogeny for the genus or the American Myrtinae has yet been proposed. Seed coat characters in combination with floral characters are useful in classifying taxa in the American Myrtinae. This revision confirms and expands this assertion. Preliminary sequence data from the ITS region of nrDNA of the American Myrtinae supports a closer relationship of Mosiera to Psidium than to Myrtus and Calycolpus. In addition, two different copies of the ITS region are present in several genera of Myrtinae.

Key words: Caribbean, ITS, Mosiera, Myrtaceae, phylogeny, seed coat