Multi-gene phylogeny of the Halosphaeriaceae: its ordinal status, relationships between genera and morphological character evolution

The halosphaeriaceous fungi constitute the largest group of marine Ascomycota found predominantly in marine environments, with few transitional species found in freshwater and brackish water habitats. It has been one of the most intensively studied groups of marine fungi, with 126 species in 53 genera. The classification of the halosphaeriaceous fungi is contentious with one school maintaining that they should be regarded as a family in the Microascales, while others continue to retain the order Halosphaeriales. To refine the phylogenetic inter-relationships among the halosphaeriaceous fungi, 36 taxa were sequenced and analysed based on three loci [nuclear small and large subunit (SSU, LSU), the second largest RNA polymerase II subunit (RPB2)]. The halosphaeriaceous fungi constitute a monophyletic group and share a common ancestor with the Microascaceae however, they share few morphological characters. In the Halosphaeriaceae the centrum tissue comprises catenophyses; asci are clavate to fusiform; ascospores are hyaline, unicellular to many septate, usually with appendages, and most are saprobic in aquatic habitats. Whereas, the peridium of the Microascaceae is carbonaceous, frequently bearing hyphal appendages or setae; asci are globose or ovoid; ascospores are reniform, often bear ornamenting ridges or wings. Genera in the Microascaceae are mainly saprobic from soil to rotting vegetation and occasionally found as pathogens, and primarily terrestrial. Based on morphological data the halosphaeriaceous taxa might be considered as a group warranting ordinal status (Halosphaeriales) and this issue is discussed in this study. Sequence data also show clearly that the genera Remispora and Ceriosporopsis are polyphyletic and we propose the erection of three new genera to accommodate C. tubulifera (Toriella), R. crispa (Kochiella) and R. galerita (Tubakiella). Bovicornua intricata is referred to the genus Ceriosporopsis. The molecular data indicate that different phylogenies based on DNA sequences support a hypothesis that ascospore appendage developments e.g. unfurling bipolar appendages, have evolved and been lost several times.