Areas of Endemism Going Underground: Obligate Groundwater‐Dwelling Copepods as a Model Group for Assessing Spatial Features of Subterranean Endemics
Emma Galmarini, Francesco Cerasoli, Barbara Fiasca, Mattia Iannella, Nataša Mori, Diana M. P. Galassi, Mattia Di CiccoABSTRACT
Aim
Groundwater ecosystems host a highly diverse and specialized biodiversity; however, current knowledge remains limited, partly due to the low accessibility of subterranean environments. We aimed to delineate Areas of Endemism (AoEs) for European groundwater copepods, concurrently developing a reproducible, conservation‐oriented workflow to individuate areas of high endemicity under sparse data availability.
Location
Europe.
Taxon
Crustacea: Copepoda.
Methods
We took advantage of the EGCop dataset, retaining 5709 occurrences across 467 obligate groundwater‐dwelling species after data filtering for taxonomic uncertainty. AoEs were delineated using a grid‐free, density‐based clustering approach (CLUENDA, DBSCAN‐based) across 60 parameter combinations. A consensus procedure was applied to identify robust AoEs, namely those emerging from ≥ 95% of parameter combinations. We also developed a species‐level Endemicity Score (ES) as a function of spatial dispersion of occurrence records. Based on ES, we derived three AoE‐level metrics, respectively representing raw, richness‐weighted and density‐weighted endemicity.
Results
We identified 17 robust AoEs across Europe (i.e., areas consistently supported across different parameter combinations), largely associated with karst regions and historically stable hydrogeological systems. These AoEs varied widely in extent, species richness and endemicity. A total of 91 point endemics (i.e., species known only from a single locality) were recorded within the identified AoEs. Endemicity patterns differed among metrics, with some areas maximizing total endemicity and others showing higher richness‐weighted or density‐weighted scores. Nonetheless, narrow‐ and point‐endemic taxa consistently shaped the observed spatial patterns of endemicity.
Main Conclusions
European groundwater ecosystems are structured into distinct centres of endemism driven by hydrogeological compartmentalization, long‐term isolation and limited dispersal. The high frequency of point endemics implies that local habitat loss may cause irreversible loss of unique lineages. By integrating grid‐free clustering, endemicity weighting and sensitivity analysis, our framework provides a reproducible and conservation‐relevant tool for identifying priority areas under uncertainty, with potential applications across other sparsely sampled subterranean taxa.