A global meta-analysis of ITS rDNA sequences from material belonging to the genus Ganoderma (Basidiomycota, Polyporales) including new data from selected taxa

GanodermaP. Karst. is a cosmopolitan genus of white-rot fungi which comprises species with highly-prized pharmaceutical properties, valuable biotechnological applications and of significant phytopathological interest. However, the status of the taxonomy within the genus is still highly controversial and ambiguous despite the progress made through molecular approaches. A metadata analysis of 3908 nuclear ribosomal internal transcribed spacer (ITS) rDNA sequences obtained from GenBank/ENA/DDBJ and UNITE was performed by targeting sequences annotated asGanoderma, but also sequences from environmental samples and from material examined for the first time.Ganodermataxa segregated into five main lineages (Clades A to E). Clade A corresponds to the core of laccate species and includesG. shanxienseand three major well-supported clusters: Cluster A.1 (‘G. lucidumsensu lato’) consists of taxa from Eurasia and North America, Cluster A.2 of material with worldwide occurrence includingG. resinaceumand Cluster A.3 is composed of species originating from all continents except Europe and comprisesG. lingzhi. Clade B includesG. applanatumand allied species with a Holarctic distribution. Clade C comprises taxa from Asia and Africa only. Clade D consists of laccate taxa with tropical/subtropical occurrence, while clade E harbours the highest number of non-laccate species with a cosmopolitan distribution. The 92Ganoderma-associated names, initially used for sequences labelling, correspond to at least 80 taxa. Amongst them, 21 constitute putatively new phylospecies after our application of criteria relevant to the robustness/support of the terminal clades, intra- and interspecific genetic divergence and available biogeographic data. Moreover, several other groups or individual sequences seem to represent distinct taxonomic entities and merit further investigation. A particularly large number of the public sequences was revealed to be insufficiently and/or incorrectly identified, for example, 87% and 78% of entries labelled asG. australeandG. lucidum, respectively. In general, ITS demonstrated high efficacy in resolving relationships amongst most of theGanodermataxa; however, it was not equally useful at elucidating species barriers across the entire genus and such cases are outlined. Furthermore, we draw conclusions on biogeography by evaluating species occurrence on a global scale in conjunction with phylogenetic structure/patterns. The sequence variability assessed in ITS spacers could be further exploited for diagnostic purposes.