RESUMO
Molecular systematic studies published during the last 15 years to clarify the phylogenetic relationships among the malaria parasites have led to two major hypotheses on the descent of Plasmodium falciparum: One supports an avian origin as a result of a relatively recent host switch, and another one favours the evolutionary development of P. falciparum together with its human host from primate ancestors. In this paper, we present phylogenetic analyses of three different Plasmodium genes, the nuclear 18 small sub-unit (SSU) ribosomal ribonucleic acid (rRNA), the mitochondrial cytochrome b (cyt b) and the plastid caseinolytic protease C (ClpC) gene, using numerous haemosporidian parasite DNA sequences obtained from the GenBank as well as several new sequences for major malaria parasites including the avian one Plasmodium cathemerium, which has never been considered in molecular phylogenetic analyses before. Most modern and sophisticated DNA substitution models based on Bayesian inference analysis were applied to estimate the cyt b and ClpC phylogenetic trees, whereas the 18 SSU rRNA gene was examined with regards to its secondary structure using PHASE software. Our results indicate that the data presently available are generally neither sufficient in number nor in information to solve the problem of the phylogenetic origin of P. falciparum.
