| Disterigma (Ericaceae) is a neotropical blueberry genus that grows in Central and South America. The majority of the species of Disterigma are at altitudinally confined to the cold and humid environments of the cloud forests and paramos, few are widespread and many are narrow endemics. The shrubs of Disterigma are typically small and have diverse growth forms that include erect, scandent, prostrate or cushion-like shrubs. As the number of species included in Disterigma increased over the years, the morphological characters that distinguished it from other inferior-ovaried Ericaceae became less clear; this notion that the morphological circumscription was too wide and that Disterigma s.l. might not be a natural group was supported by recent preliminary molecular evidence. In this study, comprehensive phylogenetic analyses incorporating both morphological and molecular data have allowed to identify a diagnosable monophyletic group, Disterigma s.s., which is the subject of a monograph. Additionally, here also is investigated the sensitivity of the data and of its derived phylogenetic hypotheses to the variation of analytical parameters. Lastly, the results of two- and one-step phylogenetic approaches (multiple alignment + tree search vs. direct optimization, respectively) are compared. Disterigma s.s. is distinguished from other taxa within Vaccinieae by the presence of a pair of bracteoles at the apex of the pedicel, which surround the calyx and which are differentiated in size from other bracts and bracteoles. Thirty-two species are recognized within Disterigma s.s., and D. bracteatum, D. pentandrum, D. rimbachii, D. trimerum, and D. ulei will be segregated from it. The monograph includes changes in the nomenclature and circumscription of three of the most widespread species of Disterigma s.s. (D. acuminatum, D. alaternoides, D. humboldtii), the resurrection of D. dendrophilum, the proposition of seven synonyms and one new combination, as well as the designation of a neotype and a lectotype. Additionally, eight new species from Colombia, Ecuador, and Peru have been discovered during this study. |
