The phylogeny of Monsonia L. (Geraniaceae)

The phylogeny of Monsonia L. (Geraniaceae) is examined. Analysis of nrDNA ITS and trnL (UAA) 5'exon-trnF (GAA) chloroplast DNA sequence data of 26 Monsonia and two outgroup Pelargonium species, suggests monophyly for the genus including the former genus Sarcocaulon (DC.) Sweet. The species of Monsonia sect. Sarcocaulon resolve as two subclades (ITS cladogram 80% and trnL-F cladogram 96%) and two additional species in an unresolved basal polytomy, in a clade with species of the sect. Olopetalum and M. senegalensis. All these species share the basic chromosome number x = 11. The remaining species have derived karyotypes of x = 12, 10, 9 or 8. Chromosome sizes vary considerably between the species, and polyploids are rare. The current infrageneric classification is discussed