PHYLOGENETIC ORDINAL PLACEMENT BASED ON RDNA SEQUENCES OF THE FRESH-WATER GENERA OPHIOCERAS AND PSEUDOHALONECTRIA

The ordinal placement of two closely related freshwater genera, Ophioc eras and Pseudohalonectria, was assessed by using phylogenetic analysi s of morphological characters, partial sequences of the large subunit ribosomal DNA and restriction site variations in the internal transcri bed spacer (ITS). The two genera have some morphological features that are used to define taxa in both the Sordariales and Diaporthales, and , hence, their phylogenetic relationships are unclear. Equally weighte d analyses of thirty-eight morphological characters produced unresolve d phylogenetic trees and unequivocal conclusions could not be drawn ba sed on the morphological data, The polymerase chain reaction-amplified ITS region was variable in length between the two genera and restrict ion sires in the ITS region were determined. Analysis of variation in restriction sites in the TTS region placed Ophioceras and Pseudohalone ctria in one clade with taxa sampled from Sordariales. About 350 basep airs of DNA sequence from the 5' end of the large subunit rDNA were al so determined. In phylogenetic analysis of the sequence data with Hypo crea lutea and Nectria cinnabarina as outgroups, Ophioceras and Pseudo halonectria showed a closer relationship to Neurospora crassa, Schizot hecium sp., and Sordaria fimicola of the Sordariales than to Cryphonec tria parasitica and Endothia gyrosa of the Diaporthales. (C) 1995 Acad emic Press, Inc.