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

Abstract

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. 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.

Convergent evolution of linked mating-type loci in basidiomycete fungi

“…The overall high degree of conservation in gene order and allele combinations of HD and well with recent analyses [7,53], it has to be noted that previous estimates for the last common ancestor of the pathogenic Cryptococci resulted in earlier divergence times ranging from 40 to 100 MYA [54][55][56][57]. Nevertheless, even if the divergence time of the ancestor of the pathogenic Cryptococci were underestimated in our analysis, this would still place the last common ancestor of the Trichosporonales, and thus the likely MAT fusion in this group, at a much earlier time point.…”

Timing the Origin ofCryptococcus gattiisensu stricto, Southeastern United States

“…This relatively recent emergence during the Pleistocene epoch is different from what has been hypothesized for other endemic mycoses, a much older fungal species dispersal resulting from mass migration of animal populations between continents ( 13 ). The idea of recent emergence also departs sharply from what has been hypothesized as a speciation attributable to prehistoric land movements, as has been proposed for larger Cryptococcus species separations ( 14 ). C. gattii sensu stricto has been found in and likely originates from South American locales ( 15 ).…”

Cryptococcusneoformans pericarditis in a lung transplant recipient: Case report, literature review and pearls

“…Human infections are caused mainly by two serotypes: Cryptococcus neoformans and Cryptococcus gattii . The latter has a geographic distribution mostly concentrated in South America and Western Northern America while the former has worldwide distribution. Risk of acquiring invasive cryptococcal disease is highest in patients receiving higher doses corticosteroids and immunosuppressive regimen not containing calcineurin inhibitors such as tacrolimus, which seem to have a protective effect against disseminated disease.…”

“…Cryptococcus neoformans is a basidiomycetous, encapsulated yeast that can be found in soil around the world . Even though it can cause disease in immunocompetent hosts, Cryptococcus neoformans often presents as an opportunistic infection in the immunocompromised, notably those with acquired immunodeficiency syndrome (AIDS) or recipients of solid (SOTR) or bone marrow (HSCT) transplants.…”