Species boundaries in the human pathogen Paracoccidioides

Area of Science:

• Mycology
• Evolutionary Biology
• Genetics

Background:

• Molecular taxonomy advances fungal speciation studies.
• Paracoccidioides spp. is hypothesized to comprise five phylogenetic species, with four forming the brasiliensis species complex.
• Incongruence exists between nuclear and mitochondrial DNA in resolving Paracoccidioides brasiliensis complex species.

Purpose of the Study:

• Investigate the source of mito-nuclear incongruence in the Paracoccidioides brasiliensis complex.
• Determine the role of hybridization and introgression in fungal speciation.
• Propose taxonomic revisions for Paracoccidioides species.

Main Methods:

• Analysis of 11 published nuclear gene fragments.
• Sequencing of 10 new nuclear non-coding loci.
• Microsatellite analysis and population genetic analyses.

Main Results:

• Mito-nuclear incongruence is attributed to interspecific hybridization and mitochondrial introgression.
• Evidence suggests possible nuclear introgression, but less extensive than mitochondrial introgression.
• Yeast morphology shows significant differences across the five Paracoccidioides species.

Conclusions:

• The Paracoccidioides brasiliensis complex divergence involved secondary contact and mitochondrial introgression.
• Species boundaries are maintained despite genetic introgression.
• Formal taxonomic recognition of four Paracoccidioides phylogenetic species is proposed.