Overall phylogenetic relationships within the genus Pelargonium (Geraniacea
e) were inferred based on DNA sequences from mitochondrial(mt)-encoded nad1
b/c exons and from chloroplast(cp)-encoded trnL (UAA) 5' exon-trnF (GAA) e
xon legions using two species of Geranium and Sarcocaulon vanderetiae as ou
tgroups. The group II intron between nad1 exons b and c was found to be abs
ent from the Pelargonium Geranium, and Sarcocaulon sequences presented here
as well as from Erodium, which is the first recorded loss of this intron i
n angiosperms. Separate phylogenetic analyses of the mtDNA and cpDNA data s
ets produced largely congruent topologies, indicating linkage between mitoc
hondrial and chloroplast genome inheritance. Simultaneous analysis of the c
ombined data sets yielded a well-resolved topology with high clade support
exhibiting a basic split into small and large chromosome species, the fil s
r group containing two lineages and the latter three. One large chromosome
lineage (x = 11) comprises species from sections Myrrhidium and Chorisma an
d is sister to a lineage comprising P. mutans (x = 11) and species item sec
tion Jenkinsonia (x = 9). Sister to these two lineages is a lineage compris
ing species from sections Ciconium (x = 9) and Subsucculentia (x = 10). Cla
distic evaluation of this pattern suggests that x = 11 is the ancestral bas
ic chromosome number for the genus.