Phylogenetic Relationships of Varieties and Geographical Groups of the Human Pathogenic Fungus Histoplasma capsulatum Darling

Abstract

The phylogeny of 46 geographically diverse Histoplasma capsulatum isolates representing the three varietiescapsulatum, duboisii, andfarciminosum was evaluated using partial DNA sequences of four protein coding genes. Parsimony and distance analysis of the separate genes were generally congruent and analysis of the combined data identified six clades: (i) class 1 North AmericanH. capsulatum var. capsulatum, (ii) class 2 North American H. capsulatum var.capsulatum, (iii) Central American H. capsulatum var. capsulatum, (iv) South American H. capsulatum var.capsulatum group A, (v) South American H. capsulatum var. capsulatum group B, and (vi)H. capsulatum var. duboisii. Although the clades were generally well supported, the relationships among them were not resolved and the nearest outgroups (Blastomyces andParacoccidioides) were too distant to unequivocally root the H. capsulatum tree. H. capsulatum var. farciminosum was found within the South American H. capsulatum var.capsulatum group A clade. With the exception of the South American H. capsulatum var. capsulatumgroup A clade, genetic distances within clades were an order of magnitude lower than those between clades, and each clade was supported by a number of shared derived nucleotide substitutions, leading to the conclusion that each clade was genetically isolated from the others. Under a phylogenetic species concept based on possession of multiple shared derived characters, as well as concordance of four gene genealogies, H. capsulatum could be considered to harbor six species instead of three varieties.

Geographical distribution of genetic polymorphism of the pathogenHistoplasma capsulatumisolated from infected bats, captured in a central zone of Mexico

“…In the present paper, EH-384I and 384P isolates (group II) showed diversity in relation to group I and III, and may have originated from a different phylogenetic group. In order to establish whether group II behaved as a different group, since it contained only two isolates from the same infected bat, we compared the sequences of their four gene fragments studied with the sequences of H. capsulatum isolates from different sources and origins reported by Kasuga et al [30]. Results showed that group II remained independent from the other isolates studied by Kasuga et al [30] (data not shown).…”

Cryptic Speciation in the Cosmopolitan and Clonal Human Pathogenic Fungus Aspergillus Fumigatus

“…In the combined analysis, N. fischeri is allied with the large A. fumigatus ''fumigatus'' clade. The nearest apparent outgroup of these fungi appears to be too distant to provide a well-supported root for species phylogenies, as is also true for other ascomycetes including Neurospora (Dettman et al 2003b), Coccidioides (Koufopanou et al 2001), and Histoplasma (Kasuga et al 1999(Kasuga et al , 2003.…”

Looking for sex in the fungal pathogensCryptococcus neoformansandCryptococcus gattii

“…The application of molecular analyses to natural populations eliminates the need for laboratory tester strains and allows the degree of sexual recombination or clonal propagation occurring in a population to be assessed (Kasuga et al, 1999). In ecological terms, populations are defined as a collection of organisms belonging to a single species, present in one place at one time (Callow, 1998).…”