For this study, data were collected from different types of sources.
First of all, to compile a baseline inventory of the lichens of the Dolomites, we gathered occurrence and co-occurrence data from all available literature from the 19^th century to nowadays, such as checklists, site-specific vegetation surveys and monitoring, taxonomic revisions, and distributional studies. Among them, the most exhaustive historical source is the catalog of Dalla Torre and Sarnthein (1902), from which were extracted data for more than 10,299 records referred to 885 taxa. Moreover, to expand the inventory, unpublished data from the authors of the Dolichens project, collected on previous samplings, and gray literature (such as thesis) were gathered.
Next, we focused on another essential type of data: herbarium specimens. Data were gleaned from historical herbaria, some reviewed by the authors of the Dolichens project, such as the collections of Alberto Parolini (1788-1867; Nascimbene, 2007), Francesconi Ambrosi (1821-1897; Nascimbene, 2001), or Giacomo Bresadola (1847-1929; Nascimbene, 2000). In addition, online herbaria available on GBIF (GBIF.org, 2023) were consulted, and included. Furthermore, all herbarium data of ITALIC 7.0 (Nimis and Martellos, 2023) referring to the study area are automatically integrated into the database, at each update.
Lastly, new sampling campaigns were carried out and are still ongoing, mainly in the Paneveggio-Pale di San Martino Natural Park, the Adamello Brenta Natural Park, and the Dolomiti Bellunesi National Park. They are focused on protected areas and allow the investigation of both historical sites (e.g. Arnold's localities) and new localities that have been poorly explored.
A project on the iNaturalist platform was also set up, where pictures of lichens taken by the authors of the Dolichens project will be collected. In this way we aim to enhance records for those common and easily identifiable species that are often uncollected and therefore often remain underrepresented.

Therefore, all the data collected can be resumed into four main categories:

• Floristic survey: occurrence data from checklists, floras, taxonomic revisions.
• Vegetation plot: co-occurrence data from vegetation surveys and monitoring.
• Observation: field observations, photographic materials.
• Herbarium specimen: authors' herbaria, revised herbaria, GBIF and ITALIC 7.0 herbaria.

For each record, the following information was retrieved, when possible: name of the taxon in the original source, locality, collection date or year, substrate, habitat, altitude, collector, identifier etc.
Most of the occurrences (especially those older than the 21st century) lacked original coordinates, so they were georeferenced a posteriori, using sampling maps included in the source or the textual location descriptions. The georeferencing process followed the best practices by Chapman and Wieczorek (2020). Georeferenced data is of huge importance for this study and future applications. Through that, the occurrences can be displayed on the map on the taxon pages, and it was possible to infer additional geographic data to the localities, such as elevation, administrative classification, the drainage basin, the SOIUSA classification, and the belonging to a Protect Area.

The original taxon names are periodically updated following the nomenclature of ITALIC 7.0. For some old records this was not possible, and the related data will not be included in taxonomic statistics.
Through the taxon name, other data are also retrieved directly from ITALIC 7.0, such as:

• nomenclatural data (accepted name; reference to the accepted name, basionym, synonyms);
• other data associated to each infrageneric taxon (morpho-anatomical characters and info on the ecology of each species);
• images of lichens.

All the information collected was included in a database, available online through the queries provided. The output data are downloadable in different formats (.csv, .xlsx, .ods) with the main fields in Darwin Core format.

The Dolichens database provides the most exhaustive inventory of the lichen records referred to the Dolomites, but it is not a critical checklist. Some records are doubtful and under revision, in view of the publication of the checklist of lichens of the Dolomites. In addition, the presence of duplicate data must be considered. In fact, it is common to find the duplicate exsiccata specimens in various herbaria, and often a herbarium sample is associated with literature or unpublished sampling data.

Below is the list of available fields, a brief description, and, when available, a link to the Darwin Core Identifier.