Phylogenetic relationship and molecular taxonomy of African grasses of the genus Panicum inferred from four chloroplast DNA-barcodes and nuclear gene sequences

Abstract

The genus Panicum s.l. comprises about 450 grass species in which the C4 and the C3 metabolic pathways of photosynthesis are realized. In the West African savannah, Panicum spp. and closely related taxa dominate the landscape, with species differentially adapted to drought conditions. We obtained four chloroplast DNA barcode sequences, rbcL, matK, ndhF and trnH-psbA intergenic region, for nine Panicum spp. with a focus on West African species, and we performed maximum likelihood analysis to infer their phylogenetic relationship. Furthermore the phylogenetic placement of five newly sequenced taxa was achieved using a published phylogeny of more than 300 Panicoids based on ndhF sequences. The comparison of the resulting phylogenetic tree constructed from a combination of all four barcode sequences with the one based on rbcL and matK showed that the latter combination of the two, is sufficient for the analysis. A tree constructed from amino acid sequences derived from isolated cDNAs of the nucleus-encoded phosphoenolpyruvate carboxylase displayed a similar topology. All ppc-sequences could be annotated to either ppc-B2 or ppc-aR. Moreover the inclusion of the West African Panicum species in an extensive dataset of Panicoids supports the proposition that within the subtribe Panicinae only the NAD-malic enzyme type of C4 photosynthesis is present.