Taxonomic re-evaluation of three related species of Graphium, based on morphology, ecology and phylogeny

Two fungi associated with bark beetles, Graphium pseudormiticum (described in 1994) and Rhexographium fimbriisporum (described in 1995), have two micromorphological characters in common. Both species produce conidia with conspicuous basal frills, and the conidia align in chains, despite being produced in slime. The association of G. pseudormiticum with the pine bark beetle, Orthotomicus erosus, and the association of R. fimbriisporum with the spruce bark beetle, Ips typographus, suggest ecological differences between the two fungal species. Analyses of micromorphology and phylogenetic analyses of aligned 18S and ITS sequences suggest that these two species are congeneric and should be classified in Graphium but that they represent distinct species. A collection of strains tentatively identified as Graphium spp., isolated from Ips typographus on Picea abies, Ips cembrae on Larix decidua and Tomicus minor on Pinus sylvestris in Austria share the same unusual basal conidial frills and conidial chains. Isolates from spruce were identified as G. fimbriisporum and those from pine as G. pseudormiticum. The strains from Ips cembrae on Larix decidua, distinguished by the reddish color of their colonies, microscopic structures and molecular characteristics, are described as the new species Graphium laricis sp. nov., and the close relationship of this species with the other two species is confirmed.