Phylogenetic Studies in the Paniceae (Poaceae-Panicoideae): Ocellochloa, a New Genus from the New World

The present contribution continues a critical revision of Panicum, particularly with the delimitation of incertae sedis taxa. A phylogenetic analysis of Paniceae based on cpDNA sequence data (ndhF) was performed with special emphasis on section Stolonifera of Panicum. Fourteen sequences of species of sect. Stolonifera and Echinolaena were added to a panicoid grass matrix previously published giving a total of 140 sequences. As a result, Ocellochloa is here described as a new genus including 12 new combinations: O. andreana, O. biglandularis, O. brachystachya, O. chapadensis, O. craterifera, O. irregularis, O. latissima, O. piauiensis, O. pulchella, O. rudis, O. soderstromii, and O. stolonifera. The position of Panicum venezuelae, previously placed in section Stolonifera with the above mentioned species, clearly indicates that this species is not closely related to the Ocellochloa clade. This conclusion is supported by several morphological characters, such as the presence of axillary inflorescences, cleistogamous spikelets, and glands of the lower lemma depressed, not crateriform. Ocellochloa differs from Panicum s. s. by the unilateral spikelet disposition, the smooth surface of the upper anthecium, and a C-3 photosynthetic pathway. This new genus is described and compared with other allied genera of the Paniceae.