Reticulariaceae is a well-known family of myxomycetes, the first representatives of which were described in the 17^th-18^th centuries (Leontyev et al. 2022b,Leonytev and Schnittler 2022). In 2012, the family contained three genera and 25 accepted species (Lado 2005), including the trivial Lycogala epidendrum (L.) Fr. and Tubifera ferruginosa (Batsch) J.F. Gmel. In 2012, Dmytro Leontyev (co-author) initiated a critical revision of the family, which was carried out during 2012–2023 through several projects (See Projects section). These studies increased the number of species of the Reticulariaceae to 52 (Lado 2005), the number of genera to six and one more genus, Licaethalium, was re-erected within the Cribrariaceae for species, previously classified within Reticulariaceae (Leontyev et al. 2019b). Fifteen species of the genus Lycogala, nine species and one subspecies of the genus Tubifera, three species of the genus Alwisia and two species of the genus Siphoptychium were described (Leontyev et al. 2014a, Leontyev et al. 2014b,Leontyev et al. 2015, Leontyev et al. 2019a, Lloyd et al. 2019, Leontyev et al. 2022a, Leontyev et al. 2022b, Leontyev and Schnittler 2023b, Leontyev et al. 2023). The classical species L. epidendrum and T. ferruginosa have proven to represent species complexes, which contain at least 13 and 76 biological species, respectively (Leontyev and Schnittler 2023a).

The critical re-evaluation of Reticulariaceae involved an integrative approach that combined a comprehensive morphological assessment with molecular barcoding of specimens. The molecular study, aimed primarily at identifying operational taxonomic units, but also at tracing phylogenetic relationships between them, covered almost the entire collection. In this regard, the material of the ten-year critical revision of Reticulariaceae represents the set of data unprecedented in terms of depth of study and accuracy of identification. Until now, these data had only been available as supplementary files in respective publications, making it inaccessible for broader analysis. In this paper, we present a dataset "Barcoded Reticulariaceae of the World" containing all this information, which we have now published on GBIF (Leontyev and Yatsiuk 2023) in compliance with FAIR principles (findable, accessible, interoperable, reusable). In the dataset, we provide data on 523 myxomycete records on 41 species and one subspecies of Reticulariaceae and two species of Cribrariaceae. Amongst them, 36 collections represent nomenclatural types. Nearly all (520, 99.4%) collections are accompanied with geographic coordinates; 446 (85.3%) of collections are barcoded by at least one marker gene, including 18S rDNA gene – 435 (83.2%), elongation factor 1α gene (EF1α) – 68 (12.9%) and the mitochondrial cytochrome oxidase subunit I gene (COI) – 58 (11.0%).

The primary goal of the database is to make data on the global distribution of Reticulariaceae species available for broader studies. Significant changes in the taxonomy of this family due to its critical revision have not yet been incorporated into identification literature. Species described during last several years are not yet represented in the GBIF or they are represented only by data, provided by non-institutional research via iNaturalist and, thus, not supported by molecular data or microscopy. Another problem is that many ‘classical’ species, such as Tubifera ferruginosa, T. casparyi (Rostaf.) T. Macbr., T. microsperma (Berk. & M.A. Curtis) G.W. Martin, Lycogala epidendrum, and L. exiguum Morgan have been redefined more narrowly, based on molecular data. Consequently, their geographical distribution appeared to be more limited than previously believed and available data on the distribution of these taxa should, therefore, be used with caution. Our dataset offers reliable information about the distribution of both recently-described and revised species, providing data, confirmed through molecular barcoding and meticulous morphological studies.

In our barcoding project, we thoroughly examined all the herbarium specimens available in various collections (these were around 30 herbaria and private collections from Germany, US, Costa Rica, Australia and other counties, listed in publications, cited above). Consequently, the distribution of species, based on the number of specimens, can offer a somewhat biased, yet valuable indication of their global prevalence. The species with the highest abundance (see the Taxonomic coverage secion) are L. epidendrum and T. ferruginosa. This should not come as a surprise since both species were described in the 18^th century and are found worldwide. However, these species are followed in the abundance list by Siphoptychium reticulatum Leontyev, Schnittler & S.L. Stephenson, T. vanderheuliae S.J. Lloyd, Leontyev & Dagamac, L. leopardinum Leontyev, Ishchenko, Schnittler & E. Johannesen and T. montana Leontyev, Schnittler & S.L. Stephenson. All of these taxa are relatively recent discoveries, all made within the scope of our ten-year project (Leontyev et al. 2015, Leontyev et al. 2019a, Leontyev et al. 2023). It is reasonable to assume that species previously unknown to science before our studies are not necessarily rare. The 'invisibility' of these species to taxonomists before the start of our project can be attributed solely to the limitations of the morphological criteria that were initially used to distinguish taxa within Reticulariaceae. This conjecture is supported by the fact that much rarer species, such as S. casparyi and Licaethalium olivaceum (Ehrenb.) Rostaf., which exhibit distinct morphological characteristics, were described as early as the 19^th century (Lado 2005, Leontyev et al. 2019b). By adopting an integrative approach, at the core of which was the quest for morphological features correlated with molecular barcoding data, we were able to delimit species previously unknown to science that are widespread in extensively studied regions like Europe and North America (Leontyev et al. 2014b, Leontyev et al. 2015, Leontyev et al. 2023).

The percentage of newly-discovered species in herbarium material obtained from various continents is an intriguing aspect. Australia stands out as the leader in this regard, with a remarkable 88% of the Reticulariaceae specimens collected in the country turning out to be new species. Nevertheless, Europe and North America also present impressive results, with 52% and 51%, respectively. These values are probably biased, primarily because we did not include a proportionate number of specimens from L. flavofuscum (Ehrenb.) Rostaf., Reticulara jurana Meyl., R. lycoperdon Bull., and R. splendens Morgan in our studies. This omission occurred because these species exhibit clear morphological distinctions and were found to be taxonomically uniform, based on the sequencing of marker genes. Consequently, the abovementioned percentage of novelty within the studied collections is somewhat inflated. However, as a relative assessment, it can still offer valuable insights and this supposition gains support from the independent evidence of a unique myxomycete flora in Australia (Lloyd 2022).

Authors express their deep gratitude to all colleagues, both with and without institutional affiliation, as well as to the workers of herbaria, who provided us with valuable collections of myxomycetes.