Taxonomic Studies in the Miconieae (Melastomataceae). IV. Generic Realignments Among Terminal-flowered Taxa

Abstract

Rapid diversification and high levels of homoplasy have combined in Miconia and relatives to make generic delimitation extremely difficult. Historically, the morphologically divergent members of particular clades have been recognized as segregate genera, leaving a diverse and paraphyletic remnant within Miconia. Here the monophyly and cladistic relationships of the commonly recognized terminal-flowered genera of Miconieae are investigated, and a provisional generic classification is constructed. Recognized genera include: Anaectocalyx, Calycogonium (including Mommsenia, and a few species of Clidemia and Ossaea), Clidemia (including Heterotrichum, Miconia sect. Octomeris p.p., Myrmidone, and a few species of Tococa), Conostegia, Leandra (including Platycentrum, Pleiochiton, and several species of Ossaea and Clidemia), Pachyanthus (including Miconia lundelliana), Tetrazygia (including Tetrazygiopsis and several species of Miconia), Tococa (including Microphysca), and Miconia (including Charianthus, Ossaea sect. Octopleura, Icaria, and a few species of Clidemia). It is hypothesized that all of the above, except Miconia, represent monophyletic groups. Most species of Miconia likely are members of a single clade, but a few primitive members of this genus may belong to isolated clades, or clades whose derived species are placed in other genera, making Miconia paraphyletic. It may eventually be possible to realign and/or segregate some of these basal lineages within Miconia. However, at this time high homoplasy levels and lack of clear morphological gaps between basal members of the various lineages combine to make phylogenetic decisions very difficult. Although not fully phylogenetic, the proposed generic classification is considered an improvement of the present system, basically that of Cogniaux, in that the artificial and polyphyletic genera Clidemia sensu lato, Calycogonium sensu lato, Ossaea, and Charianthus are abandoned. The traditional maintenance of these genera has resulted from selected weighting of variable features such as petal shape, apex, and color, along with the confusion of terminal with axillary inflorescences. Nomenclatural changes have been avoided with the exception of Calycogoniumapleurum, C. lomensis, C. reticulatum, C. tetragonolobum, Clidemia angustilamina, Leandra alloeotricha, L. glomerata, L. hirsuta, L. inaequidens, L. krugiana, L. krugii, L. lima, L._limoides, L. pratensis, Miconia coccinea, M. corymbosa, M. leblondii, M. purpureus, M. fadyenii, M. neomicrantha, and Pachyanthus lundellianus.