and P. ovale as being more closely related to each other than to P. vivax. This is consistent with the proposed Asian origin of P. vivax. Although bird malaria species use a variety of mosquito vectors from the genera Aedes, Anopheles, Culex, Culiseta, Mansonia and Psorophora, all mammalian species use vectors only from the genus Anopheles. This host switch seems to have been associated with a specialization with a particular genus of mosquito. The ability to store haemozoin appears to have evolved only once in the common ancestor of Haemoproteus, Hepatocystis and Plasmodium. A study of the relationships between Haemocystis, Haemoproteus, Leucocytozoon and Plasmodium suggests that (1) Leucocytozoon is basal (2) Haemoproteus is a sister clade to the remainder (3) Parahaemoproteus is a sister to Plasmodium and (4) Haemocystis is nested within Plasmodium. As before the bird/lizard species form a distinct clade. In birds the Haemoproteus and Leucocytozoon species rarely change transmission area. These parasites are restricted to one resident bird fauna over a long evolutionary time span and are not freely spread between the continents with the help of migratory birds. Lineages of the genus Plasmodium in contrast seem more freely spread between the continents. This suggests that the origin on the genus Plasmodium may have coincided with the ability to transfer between avian hosts more easily than the other genera. An analysis of a large number of genera suggested that the taxonomy may need revision. Leucocytozoon appears to be basal to most of the Haemosporidia. The genera Heamoproteus and Parahaemaproteus are the next most basal clade. At least one species in the genus Heamoproteus grouped with the main Plasmodium clade. Within the Plasmodium clade lay the genera Hepatocystis, Nycteria and Polychromophilus. Plasmodium odocoiliei appeared to be very divergent in the clade. Within the palsmodium clade the reptile species formed one grouping while the subgenera Laverinia, Plasmodium and Vinkeia also formed subgroupings. These results if confirmed suggest that the taxonomy of the group will need substantial revision. Molecular clock estimates All dates estimated so far using a molecular clock should probably be regarded with some suspicion given the existing disagreements between the various authors. The branching order suggested by other analyses concurs with an analysis of the mitochondrial genes This latter paper puts the divergence between the reptile-bird and mammal clades at ± 3.2 million years ago (Mya). Other divergence times reported include P. falciparum – P. reichenowi -