1. The Evolution and Speciation of Plasmodium spp. Among Primates
Daphne Virlar-Knight
I. Introduction
III. Figures
IV. Discussion
Malaria is caused by a unicellular protozoan of the Plasmodium family, and is transported via the genus of mosquitos known as Anopheles. Over the last 40 million years, the ancestor to all plasmodia began to evolve, and go through different mechanisms of speciation.
After meta-analyzing the articles, it seems as though the researchers involved with Escalante et al. and Muehlenbein et al. are in agreement over the speciation and spread of Plasmodium spp. Specifically, the speciation of most human infecting Plasmodia went through speciation out of South East Asian species.
As mentioned in Methods, Muehlenbein et al. discovered the high rate of speciation among Plasmodia that affect South East Asian primates was 3-4x higher than any potential speciation occurring within African primates. This is important to note due to the fact that human malaria evolved from non-human primates, as evidenced by the phylogenetic trees in Figures. Because of this, the transmission of a newly diverged Plasmodium spp. from a macaque or orangutan to humans is inevitable.
To the left is a phylogenetic tree based on β-tubulin, CDC-2 – the nuclear genes tested by Escalante et al. – and the plastid gene TufA.4
Throughout the eras, the different species were spread throughout South East Asia and Africa. There, they would go on to infect many different primates. This poster will attempt to explain the evolutionary history of Plasmodium spp. – P. vivax in particular – from animal to man, and from SE Asia to Africa.
Merozoites of a plasmodium infected erythrocyte bursting into the circulatory system.2
II. Methods
Escalante et al. used polymerase chain reactions (PCR) to isolate and mass produce the cytochrome b gene, in hopes that it would show P. vivax as an ancestral lineage in the phylogenetic tree of Plasmodium spp. When that proved P. vivax to not be a base species, they moved on to testing two nuclear genes, and a plastid: -tubulin, CDC-2, and TufA. After analysis, the macaque origin (Asia) posed most likely for P. vivax, based on a goodness of fit test that was statistically different from the hominoid origin (Africa) that was also tested.
Muehlenbein et al. similarly used PCR, but instead looked Cox I (mtDNA), Cox III (mtDNA) as opposed to the nuclear genes Escalante et al. screened for. Additionally, they also tested the nuclear genes AMA-1, and MSP-1. These were then compiled into a Bayesian phylogenetic analysis, to create the phylogenetic tree seen on the right. Amongst other analysis, it was shown that Plasmodium spp. (in SE Asia) may be going through speciation up to four times faster than species that affect African mammalian hosts.
V. References
"Do All Mosquitoes Transmit Malaria?" World Health Organization.
N.p., Jan Web. 12 Apr
"BioQuick News--Life Science News from Around the Globe." Deadliest
Malaria Parasite Uses Anti-Sense Long Noncoding RNAs (lncRNAs) to Specifically Regulate and Periodically Switch Expression of Single Members of Its ~50-var-Gene-Family to Avoid Detection by Human Immune System. BioQuick News, 25 Feb Web. 10 Apr
Muehlenbein, Michael P. et al. “Accelerated Diversification of Nonhuman Primate Malarias in
Southeast Asia: Adaptive Radiation or Geographic Speciation?” Molecular Biology and Evolution 32.2 (2015): 422–439. PMC. Web. 13 Apr
Escalante, Ananias A. et al. “A Monkey’s Tale: The Origin of Plasmodium Vivax as a Human
Malaria Parasite.” Proceedings of the National Academy of Sciences of the United States of America (2005): 1980–1985. PMC. Web. 18 Apr
Above is an illustration of the malarial parasites divergence over the course of millions of years, as studied on the island of Borneo.3 Species affecting orangutans are in red, macaques in blue.