Cryptic speciation and recombination in the aflatoxin-producing fungus Aspergillus flavus

Abstract

Aspergillus flavus, like approximately onethird of ascomycete fungi, is thought to be cosmopolitan and clonal because it has uniform asexual morphology. A. flavus produces af latoxin on nuts, grains, and cotton, and assumptions about its life history are being used to develop strategies for its biological control. We tested the assumptions of clonality and conspecificity in a sample of 31 Australian isolates by assaying restriction site polymorphisms from 11 protein encoding genes and DNA sequences from five of those genes. A. flavus isolates fell into two reproductively isolated clades (groups I and II). The lack of concordance among gene genealogies among isolates in one of the clades (group I) was consistent with a history of recombination. Our analysis included five strains of the closely related industrial fungus A. oryzae, all of which proved to be clonally related to group I.We applied the tools of evolutionary biology to analyze three closely related fungal species of the genus Aspergillus that are important in food safety and production, addressing questions about reproductive mode and phylogenetic relationships that relate to biological control and regulation in the food industry.

Botryosphaeriaceae associated with Terminalia catappa in Cameroon, South Africa and Madagascar

“…The gene genealogies across the five different loci were not different, as illustrated by the similarity in the sums of the length of the gene trees for the observed and resampled data. Under these conditions, a recent clonal mutation, most likely due to geographical and host isolation (Geiser et al 1998), provides the best explanation for these results.…”

Genome sequencing and analysis of Aspergillus oryzae

“…Our EST analysis shows that the expression profile in solid-state cultivation is similar to that observed when a carbon source is omitted 21 . These reports suggest that the acquired foreign DNA has been rearranged in a short period of time by large-scale solid-state cultivation since A. oryzae was domesticated from an ancestor of A. flavus 22 .…”

Eukaryotic microbes, species recognition and the geographic limits of species: examples from the kingdom Fungi

“…A fungal example is provided by the morphological species, Aspergillus flavus. Only after this fungus was shown to embrace at least four phylogenetic species (Geiser et al 1998) was it possible to find diagnostic phenotypic characters for each phylogenetic species . Second, Finlay & Fenchel also note that members of different sibling phylogenetic species from different geographic regions may still be able to mate (Coleman et al 1994;Stoeck et al 1998), implying that they are truly one biological species.…”