Diana Maria Paola Galassi

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.

A tribute to Raymond Rouch, a renowned researcher in groundwater ecology, focuses on scientific and cultural aspects of his work filled with new ideas and stimulating results addressed to the following topics: (a) the taxonomy and systematics of copepod crustaceans, particularly Harpacticoida and Gelyelloida, found in groundwater habitats; (b) the groundwater ecology, where innovative ideas, new methods of research, and scientific results helped to promote a modern new groundwater ecology; and (c) the insertion of a hydrogeology approach insofar as the research in ecology required identifying the origin and dynamics of groundwater flows in karst systems in particular. As an addition, the story of the famous Bou–Rouch pump is presented. The interest in various scientific fields reveals Rouch’s broad erudition. He was an excellent draftsman and expressed himself through painting, inspired by Max Ernst and Salvador Dali. The appreciation for the scientific work of Raymond Rouch by the community is illustrated through the dedication to him of 20 species named in his honor. Two annexes include Rouch’s list of publications and a list of the new taxa he described.

Groundwater ecosystems host unique and functionally important fauna, yet they are increasingly threatened by salinization driven by natural processes and human activities. Despite growing attention to groundwater quality, little is known about how salinity shapes subterranean crustacean assemblages on small carbonate islands. This study examines how groundwater salinity influences the distribution of stygobitic (i.e., highly specialized organisms that complete their whole life cycle in groundwater) and non-stygobitic crustaceans in groundwater habitats of the Pianosa Island (Tuscan Archipelago, Italy). We sampled ten bores, measured key physicochemical parameters, and identified crustaceans collected through on-site filtration. Principal Component Analysis and Canonical Analysis of Principal coordinates highlighted a clear spatial pattern of crustacean assemblages along a salinity gradient: stygobitic species occurred only in low- and intermediate-salinity bores while non-stygobitic taxa dominated sites with elevated electrical conductivity and high Na⁺ and Cl⁻ concentrations. The most saline bore contained no stygobitic species. Insights from this study point to salinity as a key driver of groundwater biodiversity on small Mediterranean islands and highlight the vulnerability of stygobitic fauna to ongoing salinization.

At continental to global scales, energy‐related predictors relate positively to regional species richness, often explaining much of its variation in different ecosystems. However, the influence of energy on local species richness (LSR) has received much less attention. In aquatic ecosystems, LSR is predicted to increase with increasing catchment terrestrial productivity. Greater food resources resulting from increased terrestrial subsidies of nutrients and organic matter to the stream can support more individuals, thereby enabling more species to attain viable local populations, a hypothesis known as the more‐individuals hypothesis (MIH). We used generalized linear models and variance partitioning to quantify the unique and shared effects of nine local predictors and nine catchment predictors on LSR of hyporheic communities sampled at 228 sites in tropical New Caledonia streams. We found that productivity proxies, including the proportions of peridotite and bare soil in the catchment, and the normalized difference vegetation index (NDVI), correlated strongly with proxies of sediment metabolism (dissolved oxygen and pH), which in turn accounted for much of the variation in LSR. However, the positive relationship between LSR and catchment productivity, and the resulting dominance of shared effects of local and catchment predictors, were largely driven by fast‐growing taxa. Their richness and abundance increased monotonically with increasing catchment productivity. The LSR of slow‐growing taxa was largely explained by local predictors, and it showed a weak, hump‐shaped relationship to catchment productivity. The additional food resources from more productive catchments could either not be assimilated by slow‐growing taxa or were monopolized by fast‐growing taxa. Hence, other processes than those underlying the MIH, including the competitive ability of taxa to acquire available resources, likely play a role in controlling the species‐energy relationship in hyporheic invertebrate communities.

Caves are recognized as biodiversity hotspots for groundwater fauna, including obligate groundwater-dwelling copepods (Crustacea: Copepoda), exhibiting high species richness, endemism, and phylogenetic rarity. However, the extent to which caves alone provide a representative estimate of copepod species richness in karst areas remains uncertain. Taking advantage of the recently published EGCop dataset, the first expert-validated, Europe-wide occurrence dataset for obligate groundwater-dwelling copepods (hereinafter, GW copepods), this study investigates the distribution of GW copepods into karst areas, comparing species richness in caves versus other karst groundwater habitats ( e.g. , springs, karst streams, artificial wells), within and among the European karst units. The main aims are: (i) identifying karst areas which represent hotpots of GW copepod species richness; (ii) assessing to which extent caves, as open windows to the subterranean environments, contribute to define hotspots of GW copepods’ species richness into karst areas across Europe. EGCop comprises 6,986 records from 588 copepod species/subspecies distributed among four orders: Cyclopoida (3,664 records, 184 species), Harpacticoida (3,288 records, 395 species), Calanoida (32 records, seven species), and Gelyelloida (two records, two species). To perform geospatial analyses, we filtered the dataset by: (i) selecting only the records with spatial uncertainty in the associated coordinates lower than 10 km; (ii) searching for those records falling within, or very close to, the polygons representing European karst areas. Species richness hotspots were then estimated through geospatial analyses in geographic information system (GIS) environment. Within the selected records, those specifically referring to karst habitats (2,526 records, 369 species) are primarily represented by Harpacticoida (1,199 records, 228 species) and Cyclopoida (1,293 records, 132 species). Among species collected from karst habitats, records from caves (1,867, 73.9%) belong to 318 species (Harpacticoida = 189, Cyclopoida = 122, Calanoida = 7), representing 86.1% of the total species richness of karst habitats. Geospatial analyses reveal that the European hotspots of GW copepods’ species richness recorded exclusively in caves reflect the spatial arrangement of postglacial refugia in southern karst regions, though representing a subset of the broader diversity found across all karst groundwater habitats. Our findings highlight that the contribution of cave systems in groundwater biodiversity assessments and related conservation planning may vary depending on the evolution and morphologies of the target karst regions—often pointing to a high representativeness of caves for subterranean biodiversity, sometimes revealing their lower explanatory power within the broader karst systems.

This study explores the metabolic response and carbon budget of two cyclopoid copepod species, Diacyclops belgicus Kiefer, 1936 (a stygobitic, groundwater-adapted species) and Diacyclops crassicaudis crassicaudis (Sars G.O., 1863) (a stygophilic, predominantly surface-associated species). We measured oxygen consumption rates (OCRs), carbon requirements (CRs), ingestion (I) rates, and egestion (E) rates at 14 °C and 17 °C, representing current and predicted future conditions in the collection habitats of the two species. Diacyclops belgicus displayed OCRs (28.15 and 18.32 µL O₂/mg DW × h at 14 and 17 °C, respectively) and carbon budget (CR: 0.14 and 0.10 µg C/mg × d at 14 and 17 °C) lower than those of D. crassicaudis crassicaudis (OCR: 55.67 and 47.93 µL O₂/mg DW × h at 14 and 17 °C; CR: 0.3 and 0.27 µg C/mg × d at 14 and 17 °C). However, D. belgicus exhibited metabolic rates and carbon requirements comparable to those of other epigean species, challenging the assumption that low metabolic rates are universal among stygobitic species. Temperature variations did not significantly affect the metabolic responses and carbon requirements of the two species, suggesting that they may cope with moderate temperature increases.

Mires are significant C-sinks and important habitats for biodiversity conservation. Particularly in the Alpine peatlands, grazing and trampling cause mires to degrade, causing changes in plant communities that increase bulk density, peat erosion, and nutrient excesses. We took sixteen samples of epipelic and epiphytic diatoms from mire pools subjected to varying degrees of grazing in the Adamello-Brenta Nature Park (Trento, Italy). We identified >100 diatom species (ca. 70% included in Red List threat categories). We used nMDS to identify groups of diatom species. Their statistical significance was checked with an ANOSIM and, to identify the species that contributed most to the difference between the two groups, a BEST-SIMPER procedure was carried out. The multivariate analyses allowed us to identify significant differences among the most and least grazed sites, and to select the species that contributed most to this distinction. We confirmed that some species were more frequent and abundant in the most grazed sites and behaved as opportunists in the presence of a greater nutrient input, to the detriment of rare and sensitive species, which were more numerous and abundant in the less grazed sites. We provided useful information on grazing effects, underlining the importance of managing and protecting habitats of unique environmental value.

Despite the recognized ecological significance of hyporheic zones, biological investigations into their ecology, especially concerning functional diversity, remain limited. This is particularly true for copepod assemblages, abundant in the transitional zone between groundwater and surface waters, requiring more thorough exploration. To bridge this knowledge gap, our study extensively monitored a hyporheic zone within a mountain creek and examined nine functional traits across twelve copepod species found in this environment. Through the application of RLQ and fourth-corner analysis, as well as functional diversity indices including functional richness, evenness, divergence, and dispersion, we aimed to establish links between functional traits and environmental factors. Our findings revealed relationships between environmental features—specifically electrical conductivity, pH, and ammonium concentration—and the trait composition of copepod assemblages, which were influenced by species abundances. Considering the intimate connection between functional traits and ecosystem services, assessing functional diversity within hyporheic zones offers valuable insights into its functionality in terms of services rendered. This study emphasizes the importance of understanding and managing functional diversity in hyporheic zone dynamics to ensure the health and stability of ecotones and, by extension, riverine and groundwater ecosystems.

Microplastic (MP) pollution is a growing concern in every known ecosystem. However, MP presence in groundwaters and the ecological impact they can have on groundwater fauna is still poorly investigated. Here, we assess the presence of MPs in three Italian groundwater bodies, comprising two karst caves and two monitoring bores of a saturated alluvial aquifer. In addition to water samples, groundwater invertebrates were collected to assess their potential ingestion of MPs. For water samples, chemical characterization of polymers was done by Fourier Transform Infrared Spectroscopy (FTIR) 2D imaging, while fauna samples were analyzed with a tandem microscopy approach (fluorescence microscopy and FTIR). The abundance of MPs in water samples varied from 18 to 911 items/L. The majority of MPs were fibers (91%), with a mean size in the range of 100 µm and 1 mm. Black, red, and blue were the most abundant colors (30%, 25%, and 19%, respectively). The most abundant polymer was artificial/textile cellulose (65%), followed by PET (21%). MPs were found in every groundwater taxon. Pellets were the most abundant in each specimen (87% on average), while the largest were fragments, with a mean dimension of 26 µm. Cellulose was found to be the most abundant polymer (51%). This study is the first to highlight the presence of MPs ingested by groundwater fauna. Further investigations are urgently required to assess the potential ecological impact MPs can have on the resident fauna in these sensitive ecosystems.