Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 8/20/1998
Publication Date: N/A
Technical Abstract: The evolutionary history of the Gibberella fujikuroi species complex and related species was investigated by maximum parsimony analysis of DNA sequences from multiple loci. Gene trees inferred from the exons and introns of three nuclear genes [Beta-tubulin, calmodulin, and translation elongation factor EF-1alpha], mitochondrial small subunit rDNA, and 5' portion of the nuclear large subunit 28S rDNA were largely concordant and, in a combined analysis, provide strong statistical support for a phylogeny consistent with species radiations in South America, Africa, and Asia. The American clade is a monophyletic sister-group of an African-Asian clade. Africa is the most phylogenetically diverse area examined with 20 species, followed by America (14 species) and Asia (9 species). The biogeographic hypothesis proposed from the phylogenetic evidence is based primarily on the formation of natural barriers associated with the fragmentation of the ancient super-continent Gondwanaland. Discordance of the nuclear ribosoma internal transcribed spacer (ITS) based tree with gene trees from the other loci sequenced is due to nonorthologous ITS2 sequences. Remarkably, the data indicate the major ITS2 type has switched between a type I and type II sequence at least three times during the evolution of the G. fujikuroi complex, but neither type has been fixed in any of the species examined. Thirty-three of the 52 species included in this study represent either new species (30 species), new combinations (2 species), or a rediscovered species. The results further indicate that traditional sectional and species-level taxonomic schemes for this lineage are artificial and a more natural classification is proposed.