Morphology and molecules: the Sebacinales, a case study

Morphological and molecular discrepancies in the biodiversity of monophyletic groups are challenging. The intention of this study was to find out whether the high molecular diversity in Sebacinales can be verified by micromorphological characteristics. Therefore, we carried out molecular and morphological studies on all generic type species of Sebacinales and additional representative taxa. Our results encouraged us to disentangle some phylogenetic and taxonomic discrepancies and to improve sebacinalean classifications. This comprises generic circumscriptions and affiliations, as well as higher taxon groupings. At the family level, we redefined the Sebacinaceae, formerly the Sebacinales group A, and set it apart from the Sebacinales group B. For taxonomical purposes, it seems appropriate to refer Paulisebacina, Craterocolla, Chaetospermum, Globulisebacina, Tremelloscypha, and Sebacina to the Sebacinaceae and Piriformospora, and Serendipita to the Sebacinales group B. At the lower taxonomic level, we propose within the Sebacinaceae (1) to introduce Paulisebacina for Sebacina allantoidea, (2) to transfer Efibulobasidium rolleyi into a new monotypic genus, Globulisebacina, (3) to include Tremellostereum in Tremelloscypha, (4) to transfer Sebacina amesii into Tremelloscypha, (5) to combine S. helvelloides and S. concrescens in their own genus, Helvellosebacina, (6) to transfer Tremellodendron spp. into Sebacina, (7) to define S. epigaea s.str. without cystidia and flagelliform dikaryophyses, but with star-shaped resting spores, and (8) to separate S. cystidiata with simultaneously irregular germinating spores and inconspicuous cystidia, and S. flagelliformis with flagelliform dikaryophyses from S. epigaea s.str. Additional clades in Sebacina, based on molecular differences, cannot be distinguished morphologically at present.