species infect the bonobo (Pan paniscus) and these are related to the P. malariae/P. brazillium clade. The species P. gonderi appears to be the closest relation to the Asian clade. Plasmodium malariaePlasmodium malariae has been considered to be closely related to Plasmodium brasilianum and Plasmodium rhodiani. These species may be a single species with multiple hosts. Because the number of strains that have examined to date remains small, retirement of the brasilianum and rhodiani species names to junior synonym status should probably be delayed. Rodent species Although the branching order among the mammalian clades has not yet been determined the branching order in the rodent infections species has been studied. The rodent parasites (P. berghei, P. chabaudi, P. vinckei and P. yoelii) seem to form a distinct clade. P. berghei and P. yoelii appear to be sister species as do P. chabaudi and P. vinckei. The separation dates between P. berghei and P. yoelii has been estimated to be (95% credibility interval 2.5 - 6.0); that between P. chabaudi and P. vinckei has been estimated to be (95% credibility interval 5.5 - 12.6); and that between the P. berghei/P. yoelii and P. chabaudi/P. vinckei clades to be (95% credibility interval 9.0 - 17.5). These estimates are consistent with those from another paper that included a number of primate infecting species.P. atheruri appears to be the sister species of P. vinckei. Notes A recently (2009) described species (Plasmodium hydrochaeri) that infects capybaras (Hydrochaeris hydrochaeris) may complicate the phylogentics of this genus. This species appears to be most similar to Plasmodium mexicanum a lizard parasite. Further work in this area seems indicated. Unlike other eukaryotes studied to date Plasmodium species have two or three distinct SSU rRNA (18S rRNA) molecules encoded within the genome. These have been divided into types A, S and O. Type A is expressed in the asexual stages; type S in the sexual and type O only in the oocyst. Type O is only known to occur in Plasmodium vivax at present. The reason for this gene duplication is not known but presumably reflects an adaption to the different environments the parasite lives within. It has been reported that the C terminal domain of the RNA polymerase 2 in the primate infecting species (other than P. falciparum and probably P. reichenowei) appears to be unusual suggesting that the classification of species into the subgenus Plasmodium may have an