The Schizopora Xylodon case: integrating different methodologies in the study of fungal diversity

Fungi are considered key organisms across all ecosystems, mainly because of the fundamental roles they play in essential ecological processes from nutrient recycling to symbiotic associations. Fungi are also among the most numerous organisms. Despite these prominent roles, their diversity is largely unnamed, since it is estimated that only 3% to 8% of species have been described to date. Traditionally, the study of fungal species delimitation has been based upon morphological characters. However, with the development of new techniques, DNA sequences have provided more convincing evidence for species delimitation and classification. This is because changes in genetic sequences occur frequently and can be detected more easily than subtle changes in other traits, such as morphological characters, and therefore DNA sequences can reveal hidden species masked under a single species name. Despite the success of DNA sequences for documenting biodiversity, especially the ITS region of the nuclear ribosomal DNA (the barcode for fungi), taxonomists and evolutionary biologists have come to recognize the importance of including multiple and complementary sources of evidence for species delimitation in an integrative taxonomy framework. Schizopora (Basidiomycota, Hymenochaeteales) is a genus of corticioid fungi that include species of wood decomposers distributed worldwide. It is characterized by a hymenophore with pores that break apart to form teeth, among other traits. However, as a result of recent molecular studies Schizopora species were transferred into the genus Xylodon. Xylodon is considered one of the most species rich corticioid genera with more than 80 species formally recognized. During the last ten years, 14 new species have been described and 59 combinations have been proposed, which shows that Xylodon taxonomy is far from being completely known. This taxonomic instability in combination with the supposed worldwide distribution for many of the species makes Xylodon a good candidate for using an integrated taxonomy framework to study its species diversity...