Discovery of unusual anatomical and continuous characters in the evolutionary history of Conostegia (Miconieae: Melastomataceae)

Abstract

Conostegia has been traditionally defined to consist of 42 species in the tribe Miconieae. Recent phylogenetic studies have cast doubt on the monophyly of the genus and highlighted the need for a phylogenetic study focused on Conostegia. The purpose of this study was to test the monophyly of Conostegia and address relationships in the genus. We addressed the evolutionary history of Conostegia using DNA sequences from six loci. Difficulty in finding discrete characters that support clades prompted an anatomical survey of leaves and flowers as well as the exploratory use of some continuous characters. We coded as many species as possible for fifteen characters. Lastly, field work was conducted to document floral traits at anthesis due to the poor quality of preservation of flowers on herbarium specimens. Conostegia was found to be paraphyletic and composed of three main clades. The historically important characters of a calyptrate calyx and pleiostemony were found to have evolved more than once inside the Conostegia clade. Several other characters were found to support the clades we identified. The most unusual characters were mucilage inside the ovary which is here reported in the Melastomataceae for the first time, a stele inside the style which is mostly restricted to one clade of Conostegia and known only in this clade of the Melastomataceae, and herkogamy which has been lost in two clades within Conostegia. A combination of molecular phylogenetic analyses and broad morphological surveys allowed the better understanding of the evolutionary history in a clade of mostly cloud forest Neotropical trees. The need to include anatomical studies and tackle continuous characters is here demonstrated.