Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 104, Issue 37, Pages 14872-14877Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0702356104
Keywords
biogeography; evolution; pathogen; transmission; virulence
Categories
Funding
- NIAID NIH HHS [AI036629, R01 AI036629, R01 AI059176, AI059176] Funding Source: Medline
- Wellcome Trust Funding Source: Medline
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Toxoplasma gondii is a highly prevalent protozoan parasite that infects a wide range of animals and threatens human health by contaminating food and water. A markedly limited number of clonal parasite lineages have been recognized as predominating in North American and European populations, whereas strains from South America are comparatively diverse. Here, we show that strains from North America and Europe share distinct genetic polymorphisms that are mutually exclusive from polymorphisms in strains from the south. A striking exception to this geographic segregation is a monomorphic version of one chromosome (Chr1a) that characterizes virtually all northern and many southern isolates. Using a combination of molecular phylogenetic and phenotypic analyses, we conclude that northern and southern parasite populations diverged from a common ancestor in isolation over a period of approximate to 10(6) yr, and that the monomorphic Chr1a has swept each population within the past 10,000 years. Like its definitive feline hosts, T. gondii may have entered South America and diversified there after reestablishment of the Panamanian land bridge. Since then, recombination has been an infrequent but important force in generating new T. gondii genotypes. Genes unique to a monomorphic version of a single parasite chromosome may have facilitated a recent population sweep of a limited number of highly successful T. gondii lineages.
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