Phylogeny of Ophioceras spp. based on morphological and molecular data

Collections from freshwater habitats of undescribed Ophioceras-like pyrenomycetes with scolecosporous ascospores were characterized using morphological characters, restriction analysis of PCR amplified rDNA, and 18S rDNA sequences. Five species of Ophioceras were resolved and one species was excluded from the genus. Parsimony analysis of morphological characters did not resolve relationships among species of Ophioceras and Pseudohalonectria, two closely related freshwater genera. Based on phylogenetic analysis of partial 18S rDNA sequences, species of Pseudohalonectria form a sister clade to Ophioceras 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. This calls to question the reliability of the morphological and biological characters currently used to separate Gaeumannomyces from Ophioceras. In parsimony 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 using neighbor-joining methods based on various distance measures. Neither method of analysis resulted in trees that supported placement of these genera in the Sordariales where they are currently placed. Lulworthia, a genus containing marine pyrenomycetes with scolecosporous ascospores, is not closely related to Ophioceras or Pseudohalonectria and is distant from species in the 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 supported by both parsimony and neighbor-joining methods of analyses.