Diversity of fungi in the Mediterranean Sea: highlights from a comprehensive dataset of published records

Fungi constitute an essential component of marine biodiversity and contribute to the ecosystem functioning through their symbiotic interactions and cycling of nutrients. Marine fungi are commonly recorded in association with inert or living substrates, in environmental conditions ranging from shallow temperate waters to extreme habitats with low temperature, nutrients, light and/or oxygen. Species occurrence data are abundant and continuously growing, although often scattered across research articles in various fields and missing systematic archiving. The development of accessible databases with curated occurrence records is essential to highlight the biodiversity of marine fungi and support quantitative analysis of their functions.  To this end, we assembled a new dataset consisting of records of fungi from the marine environment in the Mediterranean Sea. Literature search was performed in Google Scholar by using keywords “marine”, “fungi”, “Mediterranean”, “Sea” in English, Italian, French, Spanish, and German. We manually analysed each article to check for relevance, and listed recorded fungal taxa in our dataset. Other than occurrence data and metadata, we annotated each record for its trophic behaviour and likeliness to implement it, following the criteria of FUNTRAITS. From 130 articles we manually extracted 4630 fungal records, and classified them as primary or secondary records whether they represented new observations or reported previously published records. Most fungal taxa were obtained from samples gathered in coastal environment compared to the open sea. Samples carrying the majority of fungal records were living organisms and organic natural substrates, while a minority of records was observed on organic artificial or inorganic substrates. The identification of recorded fungi was performed in most cases to the species level, with taxa belonging to Ascomycota and Basidiomycota phyla dominating the depicted biodiversity. Our study sheds light on the currently known diversity of fungi in the Mediterranean Sea, calling for increased actions to map fungi in understudied marine environments as well as more studies delving deeper on the function of fungi in their habitat.