Phylogeny of Halosarpheia based on 18S rDNA

Species of Halosarpheia, a genus of aquatic Ascomycetes, are morphologically unified by the presence of unfurling ascospore appendages. This character state may be unreliable for resolving evolutionary relationships, however, due to its likely adaptive nature. Taxonomic emphasis on unfurling ascospore appendages has led to the inclusion of species within Halosarpheia that are morphologically similar enough to confound identification, as well as those distinct enough to question their placement in the genus. Phylogenetic analyses of 18S rDNA sequences demonstrate polyphyly of the genus, with H. fibrosa, the type of the genus, resolved separately from all other species of Halosarpheia analyzed. Morphologically similar species H. retorquens, H. viscosa, H. heteroguttulata, and H. lotica are distinct species separable by RFLP analysis of the ITS1 region as well as 18S rDNA sequence analyses. Some morphological characters used to delineate species within Halosarpheia, such as ascospore guttulation pattern and number of ascospore appendages, may actually reflect generic differences that have been overshadowed by convergent evolution in appendage type.