A trnL-F based phylogeny for species of Pelargonium (Geraniaceae) with small chromosomes

Phylogenetic analysis was performed of 921 positions of trnL (UAA) 5' exon - trnF (GAA) exon chloroplast DNA regions from 68 representatives of Pelargonium sectt. Campylia, Cortusina, Glaucophyllum, Hoarea, Isopetalum, Ligularia, Otidia, Pelargonium, Peristera, Polyactium, and Reniformia, together with five putative outgroup species from sections Ciconium, Chorisma and Jenkinsonia. The total data set therefore comprised 67.2 kb of DNA sequence. Two main ingroup clades were identified: one clade contains sections Peristera, Reniformia, and Isopetalum, the other contains sections Campylia, Cortusina, Glaucophyllum, Hoar-ea, Ligularia, Otidia, Pelargonium, Polyactium and two species currently grouped in sect. Peristera. Branching order among five main clades within the latter clade was not resolved. The trnL-F sequence data support monophyly only for sections Reniformia and Hoarea, the remainder of the currently recognized sections of Pelargonium being either paraphyletic or polyphyletic. The data further suggest that sect. Polyactium is diphyletic and that sect. Glaucophyllum is nested within sect. Pelargonium. One relatively derived clade, which represents half of the genus, contains predominantly geophytic and succulent species, occurring in the geographically restricted winter rainfall region of the South African Cape. This pattern is interpreted as reflecting explosive radiation, possibly as an adaptive response to recent aridification in the western Cape.