Phylogeny of the Paniceae (Poaceae: Panicoideae) integrating DNA sequences and morphology

MORRONE, O., L. AAGESEN, M. A. SCATAGLINI, D. SALARIATO, S. S. DENHAM, M. A. CHEMISQUY, S. SEDE, L. M. GIUSSANI, E. A. KELLOGG & F. O. ZULOAGA

TUCUMAN, ARGENTINA

Workshop; XXVII International Meeting of the Willi Hennig Soci; 2008

The tribe Paniceae currently includes approx. 110 genera and 2000 species worldwide distributed. The Paniceae exhibits a great morphological and physiological variability that difficults establishing generic boundaries among its members; recent molecular studies lead to a new classification of several genera of the tribe. The present study aims to analyze all genera of the tribe combining morphological and ndhF sequence data in order to delimit the tribe within the Poaceae, and to establish generic relationships within it.             As found in earlier studies monophyly of the Paniceae was not supported. The Paniceae is divided in two major clades, recognized as the x=9 and x=10 clades. The ndhF sequences support a sister-group relationship between the x=10 clade and the tribe Andropogoneae.             The x=10 clade is defined by a 6 base pair long insertion in the ndhF sequences. The basal dichotomy divides the group into a small clade integrated by minor genera from Australia, India, and Africa, and a major clade including American taxa only, some genera, such as Paspalum and Axonopus, with a high number of species.               The distribution of the x=9 clade is mainly Pantropical. Within this clade the basal dichotomy separates a small clade including the genus Digitaria and three small genera previously related to taxa of the ‘Bristle clade’: Anthephora and related genera. This clade is well supported and defined by a 24 base pair long deletion within the ndhF sequences. Main clades within the x=9 clade are the ‘Bristle clade’ that among other genera includes Setaria, Pennisetum and Cenchrus, the PEP-ck clade, with Urochloa and genera with a similar anatomic and photosynthetic syndrome, and the Panicum clade characterized by having a NAD-me photosynthetic subtype.              Although the morphological characters were homoplastic and lower the branch supports, they proved to be useful for placing several taxa for which DNA sequence data were not available.