Continental Drift and Speciation of the Cryptococcus neoformans and Cryptococcus gattii Species Complexes.

Arturo Casadevall,John Taylor,Joudeh B Freij,Christopher Hann-Soden,J Andrew Alspaugh

doi:10.1128/msphere.00103-17

Arturo Casadevall, John Taylor + Show 3 more

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https://doi.org/10.1128/msphere.00103-17

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Abstract

ABSTRACTGenomic analysis has placed the origins of two human-pathogenic fungi, the Cryptococcus gattii species complex and the Cryptococcus neoformans species complex, in South America and Africa, respectively. Molecular clock calculations suggest that the two species separated ~80 to 100 million years ago. This time closely approximates the breakup of the supercontinent Pangea, which gave rise to South America and Africa. On the basis of the geographic distribution of these two species complexes and the coincidence of the evolutionary divergence and Pangea breakup times, we propose that a spatial separation caused by continental drift resulted in the emergence of the C. gattii and C. neoformans species complexes from a Pangean ancestor. We note that, despite the spatial and temporal separation that occurred approximately 100 million years ago, these two species complexes are morphologically similar, share virulence factors, and cause very similar diseases. Continuation of these phenotypic characteristics despite ancient separation suggests the maintenance of similar selection pressures throughout geologic ages.

Highlights

Genomic analysis has placed the origins of two human-pathogenic fungi, the Cryptococcus gattii species complex and the Cryptococcus neoformans species complex, in South America and Africa, respectively
Given the rapidly accumulating genomic information and concerns about nomenclature instability, it was recently proposed that species complex nomenclature be used such that the broad taxa C. neoformans and C. gattii will be referred to as the C. neoformans species complex and the C. gattii species complex [3], a temporary expedient that we use in this essay
The research effort launched to understand the origins of the C. gattii strains causing outbreaks among otherwise healthy humans in the Pacific Northwest of Canada and the United States revealed that the best-studied lineage of the C. gattii species complex has a center of genetic diversity that includes individuals of both the a and ␣ mating types in the rainforest of Northern Brazil [4,5,6]

Summary

Introduction

Genomic analysis has placed the origins of two human-pathogenic fungi, the Cryptococcus gattii species complex and the Cryptococcus neoformans species complex, in South America and Africa, respectively. Most pathogenic cryptococcal strains have been grouped within two species known as Cryptococcus neoformans and C. gattii, but genomic analysis reveals a complex taxonomy such that each of these taxa almost certainly includes numerous individual species [2].

Results

Conclusion