Multiple gene genealogies reveal recent dispersion and hybridization in the human pathogenic fungus Cryptococcus neoformans.

Cryptococcus neoformans (= Filobasidiella neoformans) is a significant emerging fungal pathogen of humans. To understand the evolution of this pathogen, 34 strains were obtained from various locations around the world and fragments of four genes were sequenced from each. These strains represented all three varieties and five serotypes. The four sequenced genes are: (i) the mitochondrial large ribosomal subunit RNA; (ii) the internal transcribed spacer region of the nuclear rRNA, including ITS1, 5.8S rRNA subunit and ITS2; (iii) orotidine monophosphate pyrophosphorylase; and (iv) diphenol oxidase. Phylogenetic analyses indicated considerable divergence among lineages, which corresponded to the current classification of C. neoformans into three varieties. However, there is no apparent phylogeographic pattern. Significant incongruences were observed among gene genealogies. The analyses indicated that the major lineages in C. neoformans diverged tens of millions of years ago but have undergone recent dispersion and hybridization.