Search

1. Biodiversity conservation is a central imperative of the 21st century. Subterranean ecosystems deliver critical nature’s contributions to people and harbour a broad diversity of poorly understood specialised organisms. However, the subterranean biome is still largely overlooked in global biodiversity targets. 2. We assessed how well subterranean biodiversity is represented in protected areas (Natura 2000 and Emerald networks) in two global hotspots of subterranean biodiversity (the Pyrenees and the Alps). For this, we used two comprehensive databases of terrestrial subterranean taxa, that is, leiodids (beetles) from the Pyrenees and spiders from the Alps, and identified priority areas in each region using both species richness and geographic rarity patterns. 3. Our results show the incapacity of surface-protected area networks to represent subterranean biodiversity, as more than 70% and 90% of the identified priority areas (and 40% and 22% of the species) are not effectively covered by protected areas in the Pyrenees and the Alps, respectively. 4. These findings call for developing an urgent plan for subterranean biodiversity conservation within the European Biodiversity Strategy for 2030., 1. Biodiversity conservation is a central imperative of the 21st century. Subterranean ecosystems deliver critical nature’s contributions to people and harbour a broad diversity of poorly understood specialised organisms. However, the subterranean biome is still largely overlooked in global biodiversity targets. 2. We assessed how well subterranean biodiversity is represented in protected areas (Natura 2000 and Emerald networks) in two global hotspots of subterranean biodiversity (the Pyrenees and the Alps). For this, we used two comprehensive databases of terrestrial subterranean taxa, that is, leiodids (beetles) from the Pyrenees and spiders from the Alps, and identified priority areas in each region using both species richness and geographic rarity patterns. 3. Our results show the incapacity of surface-protected area networks to represent subterranean biodiversity, as more than 70% and 90% of the identified priority areas (and 40% and 22% of the species) are not effectively covered by protected areas in the Pyrenees and the Alps, respectively. 4. These findings call for developing an urgent plan for subterranean biodiversity conservation within the European Biodiversity Strategy for 2030., 1. Biodiversity conservation is a central imperative of the 21st century. Subterranean ecosystems deliver critical nature’s contributions to people and harbour a broad diversity of poorly understood specialised organisms. However, the subterranean biome is still largely overlooked in global biodiversity targets. 2. We assessed how well subterranean biodiversity is represented in protected areas (Natura 2000 and Emerald networks) in two global hotspots of subterranean biodiversity (the Pyrenees and the Alps). For this, we used two comprehensive databases of terrestrial subterranean taxa, that is, leiodids (beetles) from the Pyrenees and spiders from the Alps, and identified priority areas in each region using both species richness and geographic rarity patterns. 3. Our results show the incapacity of surface-protected area networks to represent subterranean biodiversity, as more than 70% and 90% of the identified priority areas (and 40% and 22% of the species) are not effectively covered by protected areas in the Pyrenees and the Alps, respectively. 4. These findings call for developing an urgent plan for subterranean biodiversity conservation within the European Biodiversity Strategy for 2030.

Freshwater biodiversity loss is of concern in the Mediterranean Basin, as one of the global hotspots of biodiversity. Despite a number of faunistic and taxonomic studies that have been conducted in the last years in the African part of the Mediterranean Basin, our knowledge on freshwater biodiversity patterns in this area is still very limited. In this study, we aim to i) identify the areas with the highest potential species richness of water beetles, estimated from species distribution models using two different approaches (MaxEnt and Random Forest) and ii) conduct a gap analysis to assess the effectiveness of protected areas in the conservation of these areas. Results showed that the highest potential species richness of water beetles in Morocco occurs in the mountain areas of the Rif and Prerif, Middle Atlas and northern Central Plateau of Morocco. Among the identified priority areas (those in the top 5% of potential richness values), 21.6% are totally unprotected and ca. 65% are poorly protected (i.e., protected area extent < 25%). These results call for urgent and direct policies to protect North African freshwater biodiversity.

The climatic variability hypothesis predicts the evolution of species with wide thermal tolerance ranges in environments with variable temperatures, and the evolution of thermal specialists in thermally stable environments. In caves, the extent of spatial and temporal thermal variability experienced by taxa decreases with their degree of specialization to deep subterranean habitats. We use phylogenetic generalized least squares to model the relationship among thermal tolerance (upper lethal limits), subterranean specialization (estimated using ecomorphological traits), and habitat temperature in 16 beetle species of the tribe Leptodirini (Leiodidae). We found a significant, negative relationship between thermal tolerance and the degree of subterranean specialization. Conversely, habitat temperature had only a marginal effect on lethal limits. In agreement with the climatic variability hypothesis and under a climate change context, we show that the specialization process to live in deep subterranean habitats involves a reduction of upper lethal limits, but not an adjustment to habitat temperature. Thermal variability seems to exert a higher evolutionary pressure than mean habitat temperature to configure the thermal niche of subterranean species. Our results provide novel insights on thermal physiology of species with poor dispersal capabilities and on the evolutionary process of adaptation to subterranean environments. We further emphasize that the pathways determining vulnerability of subterranean species to climate change greatly depend on the degree of specialization to deep subterranean environments., The climatic variability hypothesis predicts the evolution of species with wide thermal tolerance ranges in environments with variable temperatures, and the evolution of thermal specialists in thermally stable environments. In caves, the extent of spatial and temporal thermal variability experienced by taxa decreases with their degree of specialization to deep subterranean habitats. We use phylogenetic generalized least squares to model the relationship among thermal tolerance (upper lethal limits), subterranean specialization (estimated using ecomorphological traits), and habitat temperature in 16 beetle species of the tribe Leptodirini (Leiodidae). We found a significant, negative relationship between thermal tolerance and the degree of subterranean specialization. Conversely, habitat temperature had only a marginal effect on lethal limits. In agreement with the climatic variability hypothesis and under a climate change context, we show that the specialization process to live in deep subterranean habitats involves a reduction of upper lethal limits, but not an adjustment to habitat temperature. Thermal variability seems to exert a higher evolutionary pressure than mean habitat temperature to configure the thermal niche of subterranean species. Our results provide novel insights on thermal physiology of species with poor dispersal capabilities and on the evolutionary process of adaptation to subterranean environments. We further emphasize that the pathways determining vulnerability of subterranean species to climate change greatly depend on the degree of specialization to deep subterranean environments., The climatic variability hypothesis predicts the evolution of species with wide thermal tolerance ranges in environments with variable temperatures, and the evolution of thermal specialists in thermally stable environments. In caves, the extent of spatial and temporal thermal variability experienced by taxa decreases with their degree of specialization to deep subterranean habitats. We use phylogenetic generalized least squares to model the relationship among thermal tolerance (upper lethal limits), subterranean specialization (estimated using ecomorphological traits), and habitat temperature in 16 beetle species of the tribe Leptodirini (Leiodidae). We found a significant, negative relationship between thermal tolerance and the degree of subterranean specialization. Conversely, habitat temperature had only a marginal effect on lethal limits. In agreement with the climatic variability hypothesis and under a climate change context, we show that the specialization process to live in deep subterranean habitats involves a reduction of upper lethal limits, but not an adjustment to habitat temperature. Thermal variability seems to exert a higher evolutionary pressure than mean habitat temperature to configure the thermal niche of subterranean species. Our results provide novel insights on thermal physiology of species with poor dispersal capabilities and on the evolutionary process of adaptation to subterranean environments. We further emphasize that the pathways determining vulnerability of subterranean species to climate change greatly depend on the degree of specialization to deep subterranean environments.

Scientists are renewing their efforts to predict the impact of climate change on biodiversity. Subterranean environments represent ideal systems to study the effect of global change in species with poor dispersal capabilities. We assess the vulnerability to climate change of the subterranean pseudoscorpion Neobisium (Blothrus) vasconicum vasconicum (Nonídez, 1925) (Neobisiidae). Thermal tolerance was measured using two complementary estimates of upper thermal limits: (i) from thermal conditions of the localities in which the species occurs (realised upper thermal limit, RUTL), and (ii) from experimentally determined thermal tolerance data (physiological upper thermal limit, PhUTL). Then, thermal safety margins (TSM) were calculated for all known localities for current and future climatic conditions, using the thermal limits from both approaches. The physiological thermal limit (PhUTL = 17.57°C) was 3.27°C higher than that obtained from the distributional and climate data (i.e., the hottest cave in which the species occurs; RUTL = 14.3°C). Regarding TSM, the future temperature (2070; RCP 8.5) of a half of the caves will be higher than the RUTL and in none of them, it would exceed the average PhUTL. This indicates that the species could have some physiological capacity to cope with warming temperatures in situ. We hypothesize that the most realistic upper thermal limit of the species could be between the RUTL and PhUTL. This study shows that complementary approaches to estimate thermal tolerance could provide more accurate predictions of the capacity to face climate change, not only in subterranean species, but also in poor dispersal species.

Coping with aridity is a physiological challenge for all organisms, including fresh-water ones. Aridity shapes distributions of aquatic species at fine and large geo-graphical scales. Specifically, for aquatic beetles, the desiccation resistance of the adults is a potential constraint for the colonisation of arid regions. We assessed the congruence between the fundamental and realised aridity niche in eight species of a Palearctic lineage of water beetles (subgenus Lumetus, genus Enochrus, family Hydrophilidae). We also estimated the relative explanatory capacity of aridity-related versus other environmental variables in species distributions. Most of the species, even those most sensitive to desiccation stress in laboratory experiments, occur in areas with high aridity within the Palearctic region. Our results suggest a lack of association between the physiological (desiccation resistance) and environmental distance matrix (realised aridity niche), or between either of these and phylogenetic distances. Aridity-related variables had generally a similar explanatory capacity in explaining the distribution of species than non-related ones. Our results indicate that desiccation resistance has not been an important physiological constraint for the colonisation of arid environments by this clade and suggest that other non-physiological factors are more important in shaping their distributions along aridity gradients. The studied beetle lineage might conserve a high basal desiccation resistance from relatively recent terrestrial ancestors, which could have provided a physiological advantage for the colonisation of arid areas. Further research could shed light on whether these unexpected results are common to other groups of aquatic insects living in arid areas or are particular to this group of beetles.

Subterranean ecosystems are among the most widespread environments on Earth, yet we still have poor knowledge of their biodiversity. To raise awareness of subterranean ecosystems, the essential services they provide, and their unique conservation challenges, 2021 and 2022 were designated International Years of Caves and Karst. As these ecosystems have traditionally been overlooked in global conservation agendas and multilateral agreements, a quantitative assessment of solution-based approaches to safeguard subterranean biota and associated habitats is timely. This assessment allows researchers and practitioners to understand the progress made and research needs in subterranean ecology and management. We conducted a systematic review of peer-reviewed and grey literature focused on subterranean ecosystems globally (terrestrial, freshwater, and saltwater systems), to quantify the available evidence-base for the effectiveness of conservation interventions. We selected 708 publications from the years 1964 to 2021 that discussed, recommended, or implemented 1,954 conservation interventions in subterranean ecosystems. We noted a steep increase in the number of studies from the 2000s while, surprisingly, the proportion of studies quantifying the impact of conservation interventions has steadily and significantly decreased in recent years. The effectiveness of 31% of conservation interventions has been tested statistically. We further highlight that 64% of the reported research occurred in the Palearctic and Nearctic biogeographic regions. Assessments of the effectiveness of conservation interventions were heavily biased towards indirect measures (monitoring and risk assessment), a limited sample of organisms (mostly arthropods and bats), and more accessible systems (terrestrial caves). Our results indicate that most conservation science in the field of subterranean biology does not apply a rigorous quantitative approach, resulting in sparse evidence for the effectiveness of

The climatic variability hypothesis predicts the evolution of species with widethermal tolerance ranges in environments with variable temperatures, and theevolution of thermal specialists in thermally stable environments. In caves, theextent of spatial and temporal thermal variability experienced by taxadecreases with their degree of specialization to deep subterranean habitats. Weuse phylogenetic generalized least squares to model the relationship amongthermal tolerance (upper lethal limits), subterranean specialization (estimatedusing ecomorphological traits), and habitat temperature in 16 beetle species ofthe tribe Leptodirini (Leiodidae). We found a significant, negative relationshipbetween thermal tolerance and the degree of subterranean specialization. Con-versely, habitat temperature had only a marginal effect on lethal limits. Inagreement with the climatic variability hypothesis and under a climate changecontext, we show that the specialization process to live in deep subterraneanhabitats involves a reduction of upper lethal limits, but not an adjustment tohabitat temperature. Thermal variability seems to exert a higher evolutionarypressure than mean habitat temperature to configure the thermal niche of sub-terranean species. Our results provide novel insights on thermal physiology ofspecies with poor dispersal capabilities and on the evolutionary process ofadaptation to subterranean environments. We further emphasize that thepathways determining vulnerability of subterranean species to climate changegreatly depend on the degree of specialization to deep subterraneanenvironments.

The immune response represents a suite of evolved traits that can involve energetic and evolutionary trade-offs with other energy-demanding and fitness-related processes. Here, we tested the hypothesis that aquatic beetles living in inland hypersaline habitats have lower immune capacity than freshwater congeners. Phenoloxidase activity, encapsulation response and antimicrobial peptide activity were compared in freshwater/hypersaline species pairs with differing osmoregulatory capacity and cuticular waterproofing properties in the genera Nebrioporus (Dytiscidae) and Enochrus (Hydrophilidae), independent evolutionary lineages that have colonised saline media separately. Hypersaline species (N. ceresyi and E. jesusarribasi) showed significantly lower phenoloxidase activity and antimicrobial peptide responses than their freshwater relatives (N. clarkii and E. salomonis). Encapsulation responses in freshwater species also appeared to be higher than in hypersaline relatives. Our results reinforce the complex nature of immune responses and suggest that adaptation to saline environments may have involved a trade-off between osmoregulation and investment in immune defences, but also are consistent with relaxed selection pressures on basal immune responses resulting from lower microbial infection load in saline habitats. In addition, the more resistant cuticle of species occupying such habitats may protect against the entry of parasites, reducing selection pressure on immunity. Because the evolution of salinity tolerance is associated with reduced immune capacity, saline specialists may be particularly vulnerable to the dilution of saline waters and consequent changes in pathogen communities and load following colonisation by more generalist microorganisms.

[EN] Freshwater ecosystems are exposed to an increasing number of stressors, challenging their biomonitoring and management. Despite recent advances in multiple-stressor research, regional-scale assessments in areas with high freshwater biodiversity and increasing anthropogenic pressure are urgently needed. We reviewed 61 studies focused on freshwater individuals, populations and communities from the Iberian Peninsula to (i) quantify the frequency of experimental approaches used (manipulative, observational), aquatic systems, biological organization levels, and types of organisms and modelled responses, (ii) identify key individual stressors and the frequency of significant positive (increase in response magnitude) and negative (decrease) effects and (iii) determine types of interacting stressors and the frequency of their combined effects. Our dataset comprised 409 unique responses to 13 types of individual stressors, 34 stressor pairs and 12 high-order interactions (3- and 4-way). We found a higher prevalence of manipulative (85 %) respect to observational studies, and a greater focus on lotic systems (59 %) and heterotrophic organisms (58 %). The most studied stressors were nutrient (Nutr), thermal (Therm), hydrologic (Hydr), ultraviolet radiation (UVR), toxic (Toxic) and salinity (Sal) stress and land-use pressure. Individual stressors showed a higher proportion of negative (34 %) than positive effects (26 %). Nutr × UVR, Toxic × Toxic, Therm × Toxic, Hydr × Toxic, Sal × Therm, and Nutr × Therm were the most studied stressor pairs. Non-interactive (50 %) and interactive responses (50 %) were balanced. Antagonistic effects (18 %) were slightly more common than synergisms (15 %), reversal or opposing. (13 %) and high-order interactions (4 %). Such proportions varied within experimental approaches, biological organization levels and organism types. Our findings are helpful to manage certain stressor combinations in Iberian freshwaters. Further efforts in Iberian mu, [ES] Los ecosistemas acuáticos continentales están expuestos a un creciente número de factores de estrés, lo que supone un reto para su monitoreo y gestión. A pesar de los recientes avances en el estudio de estresores múltiples a nivel global, resulta también necesario evaluar áreas que concentran una alta biodiversidad acuática y que están expuestas a una elevada presión antrópica. En esta revisión hemos examinado 61 estudios basados en individuos, poblaciones y comunidades de ecosistemas acuáticos continentales ibéricos para (i) cuantificar la frecuencia de la aproximación experimental usada (estudio manipulativo u observacional), el tipo de sistema acuático, niveles de organización biológica, tipos de organismos y de respuestas abarcadas, (ii) identificar estresores clave y la frecuencia de efectos positivos (aumento de magnitud de la respuesta) y negativos (descenso) y (iii) determinar las combinaciones de factores estudiados y la frecuencia de sus efectos combinados. Los estudios revisados incluyen 409 respuestas, 13 estresores individuales, 34 pares de estresores y 12 interacciones de orden superior (3er y 4º orden). Encontramos una mayor frecuencia de estudios manipulativos (85 %), en sistemas lóticos (59 %) y con organismos heterótrofos (58 %). Los estresores más estudiados fueron los nutrientes (Nutr), la temperatura (Therm), la hidrología (Hydr), la radiación ultravioleta (UVR), los tóxicos (Toxic), la salinidad (Sal) y cambios en los usos del suelo. Los efectos individuales fueron más frecuentemente negativos (34 %) que positivos (26 %). Los efectos combinados no interactivos (50 %) e interactivos (50 %) tuvieron una frecuencia similar. Los antagonismos (18 %) fueron ligeramente más frecuentes que los sinergismos (15 %), efectos reversos u opuestos (13 %) y las interacciones de orden superior (4 %). Sin embargo, estas proporciones varían notablemente entre tipos de estudios, niveles de organización biológica y tipos de organismos. Nuestros resultados son

In the context of aridification in Mediterranean regions, desiccation resistance and physiological plasticity will be key traits for the persistence of aquatic insects exposed to increasing desiccation stress. Control of cuticular transpiration through changes in the quantity and composition of epicuticular hydrocarbons (CHCs) is one of the main mechanisms of desiccation resistance in insects, but it remains largely unexplored in aquatic ones. We studied acclimation responses to desiccation in adults of two endemic water beetles from distant lineages living in Mediterranean intermittent saline streams: Enochrus jesusarribasi (Hydrophilidae) and Nebrioporus baeticus (Dytiscidae). Cuticular water loss and CHC composition were measured in specimens exposed to a prior non-lethal desiccation stress, allowed to recover and exposed to a subsequent desiccation treatment. E. jesusarribasi showed a beneficial acclimation response to desiccation: pre-desiccated individuals reduced cuticular water loss rate in a subsequent exposure by increasing the relative abundance of cuticular methyl-branched compounds, longer chain alkanes and branched alkanes. In contrast, N. baeticus lacked acclimation capacity for controlling water loss and therefore may have a lower physiological capacity to cope with increasing aridity. These results are relevant to understanding biochemical adaptations to drought stress in inland waters in an evolutionary and ecological context., Universidad de Murcia, Spanish Ministry of Economy and Competitiveness), co-financed by FEDER funds, Peer Reviewed

Physiological traits are key in determining the vulnerability of narrow range, highly specialized animals to climate change. It is generally predicted that species from more stable environments possess lower thermal tolerance breadths and thermal plasticity than those from more variable habitats – the so-called ‘climatic variability hypothesis’. However, evolutionary trade-offs between thermal breadth and its plasticity are also seen in some taxa, and the evolution of thermal physiology remains poorly understood. Subterranean environments are excellent systems for exploring these issues, being characterized by stable climatic conditions, with environmental variability increasing predictably from deep to shallow habitats. Acclimation capacity will be fundamental in determining the sensitivity of subterranean species to climate change, since they have poor dispersal capacity and limited possibility to exploit thermally different microhabitats in the uniform cave environment. We assessed critical thermal maximum (CT) and short-term heat acclimation capacity in three related beetles (Leiodidae: Leptodirini) with differing degrees of specialization to the subterranean environment (deep, shallow and facultatively subterranean, respectively) and therefore exposed to contrasting thermal variability in nature. Only the facultative subterranean species showed any acclimatory capacity, also having the highest CT across the taxa studied. However, this species might experience the highest thermal stress in its habitat under climate change. The studied subterranean specialists will be poorly able to cope physiologically with temperature increase, but in contrast exposed to lower magnitude and rate of warming. Our results fit the climatic variability hypothesis, suggesting that adaptation to cave conditions has selected against the retention of acclimation mechanisms. We show that the pathways that determine vulnerability of subterranean species to climate change depend on their d

In the context of aridification in Mediterranean regions, desiccation resistance and phys-iological plasticity will be key traits for the persistence of aquatic insects exposed to increasingdesiccation stress. Control of cuticular transpiration through changes in the quantity and composi-tion of epicuticular hydrocarbons (CHCs) is one of the main mechanisms of desiccation resistancein insects, but it remains largely unexplored in aquatic ones. We studied acclimation responses todesiccation in adults of two endemic water beetles from distant lineages living in Mediterraneanintermittent saline streams:Enochrus jesusarribasi(Hydrophilidae) andNebrioporus baeticus(Dytisci-dae). Cuticular water loss and CHC composition were measured in specimens exposed to a priornon-lethal desiccation stress, allowed to recover and exposed to a subsequent desiccation treatment.E. jesusarribasishowed a beneficial acclimation response to desiccation: pre-desiccated individualsreduced cuticular water loss rate in a subsequent exposure by increasing the relative abundanceof cuticular methyl-branched compounds, longer chain alkanes and branched alkanes. In contrast,N. baeticuslacked acclimation capacity for controlling water loss and therefore may have a lowerphysiological capacity to cope with increasing aridity. These results are relevant to understandingbiochemical adaptations to drought stress in inland waters in an evolutionary and ecological context.

Human activities are an increasing threat to Neotropical freshwater ecosystems, with the potential extinction of thousands of aquatic species. Despite this, knowledge about the effectiveness of protected area networks in protecting aquatic insects in this biogeographical region is very limited. Cuba supports the highest diversity of aquatic insects in the Antilles, with a large number of endemics. A gap analysis was conducted to assess the effectiveness of the National System of Protected Areas of Cuba (NSPAC) in the conservation of Cuban diving beetles (family Dytiscidae). This involved considering the areas with the highest potential species richness, estimated by using species distribution models with three different approaches (MaxEnt, Random Forest and Support Vector Machine), and the known localities of endemic species.The highest potential species richness of Dytiscidae in Cuba is predicted to occurin the low–medium altitude of the eastern mountain areas. Although most of these areas occur inside the NSPAC, several areas of potential high species richness are currently unprotected. It is recommended that sampling programme are carried out in areas with high predicted species richness to validate the species distribution models. The distribution of three Cuban endemic species (Copelatus barbouri, Desmopachria glabella and Celina cubensis) lies completely outside of the NSPAC. Despite their conservation interest as threatened endemic species, they are currently unprotected. To improve the conservation of freshwater biodiversity in Cuba it is recommended that (i) the NSPAC network is extended to protect áreas supporting endemic species and those with the highest potential species richness that are currently unprotected, and (ii) a whole-catchment management approach, specifically to maintain natural flows, should be adopted, especially in the mountainous areas of eastern Cuba.

Accurate assessments of species vulnerability to climate change need to consider the physiological capacity of organisms to deal with temperature changes and identify early signs of thermally induced stress. Oxidative stress biomarkers and acetylcholinesterase activity are useful proxies of stress at the cellular and nervous system level. Such responses are especially relevant for poor dispersal organisms with limited capacity for behavioural thermoregulation, like deep subterranean species. We combined experimental measurements of upper lethal thermal limits, acclimation capacity and biomarkers of oxidative stress and neurotoxicity to assess the impact of heat stress (20°C) at different exposure times (2 and 7 days) on the Iberian endemic subterranean beetle Parvospeonomus canyellesi. Survival response (7 days of exposure) was similar to that reported for other subterranean specialist beetles (high survival up to 20°C but no above 23°C). However, a low physiological plasticity (i.e. incapacity to increase heat tolerance via acclimation) and signs of impairment at the cellular and nervous system level were observed after 7 days of exposure at 20°C. Such sublethal effects were identified by significant differences in total antioxidant capacity, glutathione S-transferase activity, the ratio of reduced to oxidized forms of glutathione and acetylcholinesterase activity between the control (cave temperature) and 20°C treatment. At 2 days of exposure, most biomarker values indicated some degree of oxidative stress in both the control and higherature treatment, likely reflecting an initial altered physiological status associated to factors other than temperature. Considering these integrated responses and the predicted increase in temperature in its unique locality, P. canyellesi would have a narrower thermal safety margin to face climate change than that obtained considering only survival experiments. Our results highlight the importance of exploring thermally sensitive p