Phylogeny of Ophioceras spp. based on morphological and molecular data

Collections from freshwater habitats of undescribed Ophioceras-like pyrenom ycetes with scolecosporous ascospores were characterized using morphologica l characters, restriction analysis of PCR amplified rDNA, and 18S rDNA sequ ences. Five species of Ophioceras were resolved and one species was exclude d from the genus. Parsimony analysis of morphological characters did not re solve relationships among species of Ophioceras and Pseudohalonectria, two closely related freshwater genera. Based on phylogenetic analysis of partia l 18S rDNA sequences, species of Pseudohalonectria form a sister clade to O phioceras thereby supporting the integrity but close relationship of these two freshwater genera. Gaeumanomyces graminis falls within the Ophioceras/ Pseudohalonectria clade and is a sister taxon to a species of Ophioceras. T his calls to question the reliability of the morphological and biological c haracters currently used to separate Gaeumannomyces from Ophioceras. In par simony analyses, Ophioceras and Pseudohalonectria are more closely related to two species in the Ophiostomatales than to species in the Sordariales or Diaporthales. However, such a relationship is not evident in analyses usin g neighbor-joining methods based on various distance measures. Neither meth od of analysis resulted in trees that supported placement of these genera i n the Sordariales where they are currently placed. Lulworthia, a genus cont aining marine pyrenomycetes with scolecosporous ascospores, is not closely related to Ophioceras or Pseudohalonectria and is distant from species in t he Halosphaeriales where it is currently placed. Excluding Lulworthia, the other members of Halosphaeriales are still not monophyletic. However, they together with Micorascus and Ceratocystis formed a clade that is strongly s upported by both parsimony and neighbor-joining methods of analyses.