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 Pelarg onium sectt. Campylia, Cortusina, Glaucophyllum, Hoarea, Isopetalum, Ligula ria, Otidia, Pelargonium, Peristera, Polyactium, and Reniformia, together w ith five putative outgroup species from sections Ciconium, Chorisma and Jen kinsonia. The total data set therefore comprised 67.2 kb of DNA sequence. T wo main ingroup clades were identified: one clade contains sections Periste ra, Reniformia, and Isopetalum, the other contains sections Campylia, Cortu sina, Glaucophyllum, Hoar-ea, Ligularia, Otidia, Pelargonium, Polyactium an d two species currently grouped in sect. Peristera. Branching order among f ive main clades within the latter clade was not resolved. The trnL-F sequen ce data support monophyly only for sections Reniformia and Hoarea, the rema inder of the currently recognized sections of Pelargonium being either para phyletic 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, contain s predominantly geophytic and succulent species, occurring in the geographi cally restricted winter rainfall region of the South African Cape. This pat tern is interpreted as reflecting explosive radiation, possibly as an adapt ive response to recent aridification in the western Cape.