Phylogenetics
Among the species infecting the great apes, Plasmodium schwetzi morphologically appears to be the closest relation to P.ovale. As of 2013 this had not been confirmed by DNA studies.
The original species has been shown to be two morphologically identical forms - Plasmodium ovale curtisi and Plasmodium ovale wallikeri - which can be differentiated only by genetic means. Both species have been identified in Ghana, Myanmar, Nigeria, São Tomé, Sierra Leone and Uganda. The separation of the lineages is estimated to have occurred between 1.0 and 3.5 million years ago in hominid hosts. A second analysis suggests that these species separated 4.5 million years ago (95% confidence interval 0.5 – 7.7 Mya).
These species appear to be more closely related to Plasmodium malariae than to Plasmodium vixax.
Read more about this topic: Plasmodium Ovale