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Category: Microbial Genetics and Molecular Biology
Evolutionary History and Population Genetics of Human Malaria Parasites, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555817558/9781555813307_Chap07-1.gif /docserver/preview/fulltext/10.1128/9781555817558/9781555813307_Chap07-2.gifAbstract:
The central theme of this chapter is the molecular evolution of species of the genus Plasmodium—the experimental methods, conclusions, and confounding elements peculiar to Plasmodium. While one section of the chapter is a brief summary of studies on the evolutionary history of Plasmodium and related organisms, another is a summary of the molecular population genetics of contemporary world populations of the two most virulent human malaria parasites. In addition to humans, Plasmodium parasites infect a range of vertebrate hosts, including birds, lizards, rodents, and nonhuman primates. Malaria has also been found in African rodents, and many of the Plasmodium species have been adapted to laboratory mice and rats and used as models for human malarias. Plasmodium ovale and P. malariae cause the rarest and least virulent forms of malaria. Population studies of P. falciparum and P. vivax, however, have already yielded unexpected results, paradoxical conclusions, and questions calling for additional research. Genome-level research has made it possible to explore malaria evolution in greater depth and rigor to help complete the picture. These changes have come through malaria parasite genome projects (for P. falciparum, P. vivax, P. yoelii, and P. reichenowi) and their associated databases, access to automated DNA sequencers in most modern laboratories, an increasingly sophisticated understanding of the unusual molecular biology and evolution of the parasites, and improvements in methods of statistical inference from DNA sequence differences within and among populations.
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Summary phylogenetic tree showing the relationship between malaria parasites of mammals. Note that primate Plasmodium species are monophyletic, with the exception of the P. falciparum-P. reichenowi pairing, which is outside both rodent and primate clades. Rodent and primate parasites form monophyletic groups. Branch lengths are not proportional; only nodes with statistical support of ≥85% are shown ( Escalante et al., 1995 ; Perkins and Schall, 2002 ; Vargas-Serrato et al., 2003 ).
Summary phylogenetic tree showing the relationship between malaria parasites of mammals. Note that primate Plasmodium species are monophyletic, with the exception of the P. falciparum-P. reichenowi pairing, which is outside both rodent and primate clades. Rodent and primate parasites form monophyletic groups. Branch lengths are not proportional; only nodes with statistical support of ≥85% are shown ( Escalante et al., 1995 ; Perkins and Schall, 2002 ; Vargas-Serrato et al., 2003 ).
Unrooted tree showing the relationship of infrakingdom Alveolata (Plasmodium) to other infrakingdoms (including parasites and genomic models) within the domain Eukarya ( Cavalier-Smith, 1991 , 2004 ; Cavalier-Smith and Chao, 2003 ; Baldauf et al., 2000 ; Hedges, 2002 ; Leander et al., 2003 ).The dotted line indicates the possible sister relationship of Plantae to some protist groups ( Bastien et al., 2004 ). Branch lengths are not proportional; only nodes showing statistical support of ≥85% are included.
Unrooted tree showing the relationship of infrakingdom Alveolata (Plasmodium) to other infrakingdoms (including parasites and genomic models) within the domain Eukarya ( Cavalier-Smith, 1991 , 2004 ; Cavalier-Smith and Chao, 2003 ; Baldauf et al., 2000 ; Hedges, 2002 ; Leander et al., 2003 ).The dotted line indicates the possible sister relationship of Plantae to some protist groups ( Bastien et al., 2004 ). Branch lengths are not proportional; only nodes showing statistical support of ≥85% are included.
Placement of the order Haemosporidia with the phylum Apicomplexa and relation of Apicomplexa within Alveolata. The infrakingdom Discicristata is the sister group to Alveolata and includes several well-studied parasites. Branch lengths are not proportional; only nodes showing statistical support of ≥85% are included ( Baldauf et al., 2000 ).
Placement of the order Haemosporidia with the phylum Apicomplexa and relation of Apicomplexa within Alveolata. The infrakingdom Discicristata is the sister group to Alveolata and includes several well-studied parasites. Branch lengths are not proportional; only nodes showing statistical support of ≥85% are included ( Baldauf et al., 2000 ).
An unrooted neighbor-joining tree showing the relationships between nine P. falciparum populations. Only nodes with a bootstrap value of >75% are shown. Note that the African isolates (Zimbabwe, Congo, Uganda) from an area of high transmission show a large overall difference from the other isolates, but the relationship of the individual isolates cannot be distinguished with any statistical certainty. However, in South America, the Colombian and Bolivian-Brazilian isolates show a greater distance from each other than even overall distances from isolates from elsewhere in the world. (Figure adapted from Anderson et al., 2000 .)
An unrooted neighbor-joining tree showing the relationships between nine P. falciparum populations. Only nodes with a bootstrap value of >75% are shown. Note that the African isolates (Zimbabwe, Congo, Uganda) from an area of high transmission show a large overall difference from the other isolates, but the relationship of the individual isolates cannot be distinguished with any statistical certainty. However, in South America, the Colombian and Bolivian-Brazilian isolates show a greater distance from each other than even overall distances from isolates from elsewhere in the world. (Figure adapted from Anderson et al., 2000 .)