Evolution of the Apicomplexa: where are we now?

The Apicomplexa is the only large taxonomic group whose members are entirely parasitic and is, therefore, presumably of major interest to parasitologists. We might, for example, expect that we know a great deal about the biology of the group by now and that we have a clear phylogenetic framework within which to organize that knowledge. It might thus come as a surprise to learn that in terms of biodiversity, the Apicomplexa is actually the least-known group of all. Furthermore, the taxonomic framework for the Apicomplexa is rather tenuous in many respects. This situation is unlikely to change in the short term.