Evolution
These protozoa are mostly found in mammals. They do not appear to infect mammals of the superorder Afrotheria and infect only two species of the Xenarthra. Because of this pattern the genus may have evolved in the Northern hemisphere from a preexisting protozoan species that infected mammals.
Alternatively because a number of Australian marsupials are also infected by this genus, marsupials may have been the original hosts of this genus and the parasites were spread to the Northern hemisphere by birds.
A third possibility is that the genus originally infected birds and was spread world wide by these hosts.
A final possibility because of the existence of life cycles where both the intermediate and final hosts are reptiles, the genus may have originated in reptiles and spread from there to other genera.
The resolution of this question awaits the outcome of further molecular studies.
Read more about this topic: Sarcocystis
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