Ascomal evolution of filamentous ascomycetes: evidence from molecular data

Abstract

Phylogenetic analyses of nucleotide data from partial sequences (1150 bp) of the small subunit ribosomal DNA (SSU rDNA) were performed on 30 taxa representing several orders of Hymenoascomycetes and Loculoascomycetes. These analyses detected four major groups of filamentous ascomycetes: group 1, pyrenomycetes (Hypocreales, Microascales, Diaporthales, Sordariales) and loculoascomycetes (Pleosporales); group 2, operculate discomycetes (Pezizales); group 3, inoperculate discomycetes (Geoglossaceae); and group 4, plectomycetes (Eurotiales, Onygenales) and loculoascomycetes (Chaetothyriales). Well-supported clades, which correspond to groupings based on ascomal morphology, were resolved; however, the monophyly of the classes Hymenoascomycetes and Loculoascomycetes was rejected. The placement of the root on the filamentous ascomycete ingroup proved more problematic than resolving the ingroup relationships. Three alternative rooting possibilities, which were identified in suboptimal parsimony trees, were not significantly less likely in maximum likelihood ratio tests. Nonetheless, the most likely topology obtained from fastDNAml was identical to the most parsimonious tree. Key words: filamentous ascomycetes, Hymenoascomycetes, Loculoascomycetes, parsimony, maximum likelihood, ribosomal DNA.