An open occurrence dataset for European subterranean spiders

Spiders are remarkably diverse in caves and other subterranean habitats, where they play key ecological roles as generalist predators and strongly influence local food webs. They have been instrumental as model organisms for testing various eco-evolutionary hypotheses. Furthermore, strictly subterranean species exhibiting narrow ranges and high endemism are particularly significant for conservation planning and vulnerability assessments. Although high-quality data are essential for research on and conservation of subterranean spiders, such information remains scarce, especially regarding distribution patterns. To help fill this gap, we screened the literature, unpublished records, and open datasets to compile georeferenced occurrences of subterranean spiders across caves and other subterranean habitats throughout Europe. Based on these data—and to illustrate one potential application of the compiled dataset—we present the first prediction of subterranean spider richness patterns across Europe using stacked species distribution models. The European Subterranean Spider Dataset (ESSD) comprises 31,224 records of 637 subterranean-dwelling spider species (including morphospecies under description), covering a range of information including taxonomy, locality details (such as location name, country, geographic coordinates, type of subterranean habitat), and reference information for each record. All variables are coded using the Darwin Core Standard, ensuring interoperability with the Global Biodiversity Information Facility (GBIF) and other biodiversity databases. By enabling integration with trait and phylogenetic resources, the ESSD provides a robust framework to investigate the drivers and processes shaping subterranean biodiversity, assess vulnerability to environmental change and anthropogenic pressures, and guide future sampling to progressively reduce geographic and taxonomic gaps through open data sharing.