Susan L.
Perkins
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Malaria Systematics
My research on the evolution and
biogeography of parasites exploits the powerful techniques of molecular genetics
to pursue issues that were formerly difficult or impossible to resolve in these
taxa. Some of my work has also involved the study of the coevolution of parasites
and their hosts. Parasite-host systems are particularly intriguing because two
or more species coevolve in an antagonisitic fashion, the parasite being completely
dependent on its host(s), and the host(s) selected to eliminate the relationship.
I have used the malaria parasites ( Plasmodium and related genera),
as my model system. These parasites are very diverse (fully 170 species of Plasmodium
have been described), world-wide in distribution in many tropical, subtropical,
and temperate habitats, infect a great range of vertebrate hosts (birds, mammals,
and reptiles), and exhibit a substantial diversity of life history traits. This
great diversity of parasite-host systems allows cross-species comparisons and
phylogenetic analysis to approach important problems in biology. Molecular techniques
have recently been developed for use with human malarial parasites; I have adapted
these laboratory methods to study the great range of parasites in Plasmodium
, related genera, and more distantly related apicomplexan parasites.
The latest phylogeny based on cytochrome
b gene sequences:
Now, we are developing multiple genes for use in malaria systematics. Here
is a tree constructed with sequences from seven genes: nuclear DHFR and a cysteine
protease, mitochondrial cytochrome b and cytochrome oxidase I, and tufA, orf470
and clpC from the parasites' plastid genome.
New work is allowing us to amplify and sequence the whole mitochondrial genome
of the parasites. A preliminary phylogeny based on this ~6 kb of sequence looks
like this:
