Submitted to: American Phytopathological Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 8/29/2001
Publication Date: N/A
Technical Abstract: Multiallelic genealogies are being constructed from DNA sequences of mostly single copy nuclear genes to investigate species boundaries and the evolution of mycotoxins, host range and biogeography within the most important mycotoxigenic and phytopathogenic lineages of Fusarium. Due to the paucity of phenotypic traits, application of Genealogical Concordance Phylogenetic Species Recognition [GCPSR; Taylor et al. 2000] has revealed that this genus is about 10 times more species-rich than previously recognized using morphology alone [Nelson et al. 1983]. Although we strongly advocate GCPSR, gene-gene discordances have been encountered within all major lineages of Fusarium. One of the most striking examples is illustrated by a 19kb region of the trichothecene toxin gene cluster within the Gibberella zeae species complex. The evolutionary history of this gene cluster is highly discordant with a species phylogeny inferred from genes outside the cluster. Evolutionary processes that have contributed to the gene tree-species tree discordances within Fusarium include shared ancient trans-species polymorphisms, introgressive hybridization following secondary contact and paralogy.