Population genetics of nonclonal, nonrandomly mating malaria parasites.

In a highly controversial paper(1), Tibayrenc and colleagues have argued that clonal (asexual) reproduction may be a general phenomenon among protozoan parasites. Many parasitologists would be quite comfortable with a theory applied to Leishmania, Trypanosoma, Entamoeba and Giardia which proposes 'that uniparental reproduction is ... predominant enough in natural populations to generate clones that are stable in space and time ...' The current view is that these parasites can reproduce sexually some of the time (eg. Refs 2,3) but may not do so most of the time. What has provoked the most controversy(4-7) is the suggestion that malaria parasites can be considered as bedfellows of the above, for Plasmodium are generally thought to undergo obligate sexual reproduction in each generation. Here, Christopher Dye focuses on Tibayrenc's arguments for clonal reproduction in Plasmodium, not only because malaria parasites are at the heart of the dispute but also because an analysis of his arguments about sexually reproducing parasites carries implications for his assertions in general.