MOLECULAR PHYLOGENY OF ACREMONIUM AND ITS TAXONOMIC IMPLICATIONS

Acremonium is generally considered to be a highly polyphyletic form ge nus containing distantly related fungi. Sectional divisions within Acr emonium distinguish the clavicipitaceous grass endophytes of sect. Alb olanosa from the generally saprobic species of sections Acremonium, Ch aetomioides, Gliomastix, and Nectrioidea. In an effort to assess the p ossible number of lineages currently placed within Acremonium and to d etermine which groups of sexual ascomycetes are phylogenetically affil iated with Acremonium species, maximum parsimony and neighbor-joining analyses were performed using partial sequences of the nuclear small s ubunit ribosomal DNA (18S rDNA). Acremonium was shown to be a polyphyl etic taxon with affiliations to at least three ascomycetous orders: 1) most of the examined species from the sections Acremonium, Gliomastix , and Nectrioidea showed a relationship to the Hypocreaceae even thoug h many of these species have never been associated with any teleomorph ; 2) the grass endophytes of sect. Albolanosa and other taxa from the Clavicipitaceae formed a monophyletic group derived from within the Hy pocreales; 3) the thermophilic A. alabamense of sect. Chaetomioides wa s derived from within the Sordariales. Acremonium alternatum, the type species of the genus, was one of the species showing affiliation to t he Hypocreaceae. In order to eliminate some of the heterogeneity withi n Acremonium while also emphasizing the unique biological, morphologic al, and ecological characteristics of the grass endophytes, we are pro posing that the anamorphs of Epichloe and closely related asexual gras s endophytes be reclassified into the ne cv form genus Neotyphodium. P hylogenetic and taxonomic considerations are also presented for other taxa.