Search

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., This research was supported by a PhD grant from University of Murcia (FPU 2018) to MBC and a postdoctoral grant from Fundación Séneca (Agencia Regional de Ciencia y Tecnología, Región de Murcia) to SP.

Several field surveys at 391 freshwater localities between 1985 and 2019 were undertaken in Morocco. Altogether, our field studies identified 67 species belonging to three genera (Hydraena, Limnebius, and Ochthebius), and representing 85.89% of the Hydraenidae fauna of the country. The species Hydraena exarata Kiesenwetter, 1866 is reported for the first time from Africa, and Ochthebius (Ochthebius) thermalis Janssens, 1965 and O. (Ochthebius) grandipennis Fairmaire, 1879 are here recorded for the first time from Morocco. These findings increased the number of Moroccan Hydraenidae to 78. Ochthebius semisericeus Saint-Claire Deville, 1914 and O. viridis Peyron, 1858 are excluded from the Moroccan fauna. Furthermore, the checklist presented in this work includes 15 Moroccan endemic, 19 Ibero-Maghrebian endemic and 8 Maghrebian endemic species. A biogeographical analysis shows that the Hydraenidae from Morocco are essentially Mediterranean (89.74%), while the Palaearctic elements (7.70%) and the species with wider distributions (2.56%) are less represented, highlighting the general limited dispersion capability of Hydraenidae compared to other water beetle families. The present study can serve as the basis for future progress in the knowledge of the Moroccan Hydraenidae.

Morphologically cryptic lineages confound many estimates of global biodiversity and are often discovered in ecologically specialized taxa, subject to strong morphological constraint. Such a situation may apply in many extreme environments, including supralittoral rockpools, where dramatic fluctuations in water availability and salinity impose strong selection pressures on the inhabitants. Here we explore the genetic diversity and phylogeography of supralittoral rockpool Ochthebius beetles in the eastern Atlantic and western Mediterranean, using a combination of mitochondrial and nuclear markers and dense geographical sampling of the three recognized widespread species. Our results point to the existence of morphologically cryptic lineages within all currently named taxa and suggest that the distribution of these is linked to both historical and contemporary marine hydrogeography; a combination of ocean currents and winds apparently driving the spatial patterns observed. The main contemporary barrier to dispersal for Ochthebius is located around the Ibiza Channel, whilst the Messinian Salinity Crisis appears to have been the ultimate driver of lineage diversification in these insects. Our results show that oceanographic processes do not just shape the evolution of fully marine species, but also impact significantly on the terrestrially derived inhabitants of the coastal zone.

This checklist summarises our present knowledge on Moroccan distribution of the water beetles of five families: Gyrinidae, Haliplidae, Noteridae, Hygrobiidae and Dytiscidae. It includes all availab...

The study of the genetic makeup and demographic fate of alien species is essential to understand their capacity to recover from founder effects, adapt to new environmental conditions and, ultimately, become invasive and potentially damaging. Here, we employ genomic data to gain insights into key demographic processes that might help to explain the extraordinarily successful invasion of the Western Mediterranean region by the North American boatman Trichocorixa verticalis (Hemiptera: Corixidae). Our analyses revealed the genetic distinctiveness of populations from the main areas comprising the invasive range and coalescent-based simulations supported that they originated from independent introductions events probably involving different source populations. Testing of alternative demographic models indicated that all populations experienced a strong bottleneck followed by a recent and instantaneous demographic expansion that restored a large portion (>30%) of their ancestral effective population sizes shortly after introductions took place (

Biodiversity loss is exceptionally greater in freshwater ecosystems. To preserve such biodiversity it is crucial to know what species and habitats require greater conservation efforts. In this study, we identify the most threatened endemic sensu lato water beetles found in Morocco (i.e., Moroccan, Maghrebian and Ibero-Maghrebian endemics) using six equivalent criteria (general distribution, Moroccan distribution, species rarity, species persistence, habitat rarity and habitat loss) to rank species according to their vulnerability. From the 90 endemic species studied, only Graptodytes bremondi Guignot 1934, Esolus bicuspidatus Alluaud 1922, Enochrus blazquezae Arribas & Millan, 2013 and Elmis atlantis Alluad, 1922 were considered extremely vulnerable following our own methodology, whereas thirty six were cataloged as highly vulnerable. The protection of such species mainly requires the conservation of their habitats, particularly rivers in low lands, saline streams, peat bogs, “Sebkhas” and marshes. Most of these Moroccan habitats are very rare and/or human impacted. Nowadays, no Moroccan species of aquatic Coleoptera has legal protection, being the only conservation measure available for these species the extent to which they occur in protected areas. As a result, all these forty species should be included in the future Red List of Threatened Species for Morocco, whereas the four most threatened are proposed to be incorporated in the IUCN Red List as “Endangered B2ab (iii)”. We present the first comprehensive analysis of all endemic aquatic beetles in Morocco applying a specific methodology. Four of the ninety endemic species studied showed an extremely high vulnerability: Graptodytes bremondi Guignot 1934, Esolus bicuspidatus Alluaud 1922, Enochrus blazquezae Arribas & Millan, 2013 and Elmis atlantis Alluad, 1922. We propose all of them for inclusion in the IUCN red list as "Endangered B2ab (iii)".

Aquatic Hemiptera are barely used as "indicators" because they are considered ubiquitous organisms of great dispersal capacity and a wide range of occupied habitats. Here, we address this topic analyzing the environmental factors determining the distribution of the species found in a northeastern Moroccan basin with a strong altitudinal gradient, as well as their capability of establishing assemblages and the niche breadth for each species. Between 2014 and 2017, we sampled 55 contrasted sites representing the heterogeneity of aquatic ecosystems in the study area, where we collected a total of 27 species. The relationships between the species and environmental variables were evaluated using the STATICO methods, showing a distribution mainly influenced by the changes in flow velocity and conductivity. The Bray–Curtis dissimilarity index identified four assemblages: (a) a running species group in upper freshwater streams; (b) a middle stream group preferring less flow velocity and moderate mineralization; (c) a third group, near to the mouth, occupying moderate running or lentic brackish waters; and (d) a fourth group linked with hypersaline standing environments. The use of Indicator Species Analysis (IndVal) found few but representative species for each assemblage. The OMI applied showed that the majority of species had a high niche breadth and, consequently, a low specialization. Our results highlighted the overall poor habitat requirement and very ubiquitous character of most species found. Only some of them, mainly the endemism Aphelocheirus pemae, can be considered key for biodiversity conservation purposes because of their low niche breadth and high indicator value.

Bugio monkeys (Alouatta caraya) need their arms for locomotion, hygiene, and defence, and possess well-developed dexterity of their hands, depending on them for proper feeding. For this reason, appropriate treatment of thoracic limb fractures is not only essential but also challenging in this species. This report describes the successful treatment of a radial fracture associated with luxation of the radial head in a female, adult Alouatta caraya. The patient was admitted after a suspected traumatic event with a complete transverse fracture of the right radial diaphysis and subluxation of the ipsilateral radius head. Using a craniomedial approach to the radius, surgical stabilization was performed using a 1.7 mm micro series Fixin locking plate after open reduction in bone fragments. The patient had early use of the limb (24 hours postoperatively) and progressive improvement in its usual activities over the following weeks. Radiographic monitoring was performed at 30, 60, and 360 days postoperatively, and bone healing occurred with no complications. The treatment of fractures in primates is potentially challenging, requiring adaptation to primate anatomy and the specific living conditions of the species. Open reduction and stabilization of the radial fracture with a plate and manually reducing the luxated radial head effectively lead to long-term restoration of full function and of normal activities.

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 degree of specialization to deep subterranean environments. This information, combined with evaluation of exposure to climatic changes at their present locations, is fundamental in identifying species or populations at greatest risk., This work was supported by the Agencia Estatal de Investigación (Spain), the Spanish Ministry of Economy and Competitiveness and the European Regional Development Fund (project CGL2016-76995-P). S.P is funded by a postdoctoral grant from Fundación Séneca - Agencia de Ciencia y Tecnología de la Región de Murcia (Spain). D. S-F and M. B-C are funded by a postdoctoral and predoctoral grant from the University of Murcia (Spain) respectively. R.C and P. B-G are funded by predoctoral grants of the Spanish Ministry of Science, Innovation and Universities.

Evaluating data quality and inventory completeness must be a preliminary step inany biodiversity research, particularly in the case of insects and high biodiversityareas. Yet, this step is often neglected or, at best, assessed only for one insectgroup, and the degree of congruence of sampling effort ffor different insect groupsremains unexplored. We assess the congruence in the spatial distribution of sampling effort for fiveinsect groups (butterflies, caddisflies, dung beetles, moths, and aquatic beetles) inthe Iberian Peninsula. We identify well-surveyed areas for each taxonomic groupand examine the degree to which the patterns of sampling effort can be explainedby a set of variables related to environmental conditions and accessibility. Irrespective of the general lack of reliable inventories, we found a general but lowcongruence in the completeness patterns of the different taxa. This suggests thatthere is not a common geographical pattern in survey effort and that idiosyncraticand contingent factors (mainly the proximity to the workplaces of entomologists)are differentially affecting each group. After many decades of taxonomic and faunistic work, distributional databases ofIberian insects are still in a very preliminary stage, thus limiting our capacity toobtain reliable answers to basic and applied questions. We recommend carrying out long-term, standardised and well-designed entomolog-ical surveys able to generate a reliable image of the distribution of different insect groups. This will allow us to estimate accurately insect trends and better under-stand the full extent of global biodiversity loss., This study has been supported by the projects BioWeb (MINECO:CGL2011-15622-E BOS), BANDENCO (JCMM: POII11-0277-5747)and IBERARTRO (SBPLY/17/180501/000492) founded by European Regional Development Fund (ERDF) through the Consejería de Educación, Ciencia y Cultura, Junta de Comunidades de Castilla-La Mancha. David Sánchez-Fernández is funded by a postdoctoral contract fromthe Spanish Ministry of Science and Innovation (Ramón y Cajal program; RYC2019-027446-I

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., Part of this work was funded by the project CGL2013-48950-C2-1&2-P from the Agencia Estatal de Investigación (AEI) of Spain and the European Regional Development Fund (FEDER, EU). S.P. and D.S.-F. are funded by postdoctoral contracts from the Spanish Ministry of Science and Innovation (Juan de la Cierva-Formación, FJC2018-035577-I and Ramón y Cajal, RYC2019-027446-I programmes, respectively).

Accurate assessments of species' vulnerability to climate change require integrated measurements of its different drivers, including extrinsic (the magnitude and rate of climate change) and intrinsic factors (organisms' sensitivity and adaptive capacity). According to these factors, aquatic insects restricted to alpine ponds may be especially threatened by climate change. However, vulnerability predictions based on such an integrative approach are scarce for alpine pond taxa. We combined distributional, climatic data and experimental measurements of heat tolerance and acclimation capacity of two water beetles endemic to Sierra Nevada National Park (Spain) to evaluate different components of their vulnerability to climate change. We estimated: (i) changes in climatically suitable habitat under different scenarios of climate change and (ii) thermal safety margins (the difference between species upper thermal limits and the maximum temperatures in their current localities), for current and future conditions, and acclimation capacity, as measures of the physiological capacity to persist in situ. Species distribution models predicted a virtual loss of climatically suitable area under different climate change scenarios. Nonetheless, both taxa showed heat tolerance limits above the predicted maximum temperatures in their current localities (but no capacity to adjust such limits through acclimation). Therefore, these beetles could have the physiological capacity to deal with warming conditions in situ. We recommend concentrating conservation efforts in current localities as the most efficient management strategy for both taxa. Our results stress the importance of accounting for physiological tolerances when predicting the vulnerability to climate change in alpine freshwater biota.

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., This research was funded by the R&D&I Project CGL2013-48950-C2-2-P (J.V. and A.M.) (Spanish Ministry of Economy and Competitiveness), co-financed by FEDER funds, and a PhD Grant from the University of Murcia to MBC. S.P is funded by a postdoctoral grant from the Juan de la Cierva-Formación program (FJC2018-035577-I) by the Spanish Ministry of Science and Innovation.

1. Rivers are dynamic ecosystems in which both human impacts and climate-driven drying events are increasingly common. These anthropogenic and natural stressors interact to influence the biodiversity and functioning of river ecosystems. Disentangling ecological responses to these interacting stressors is necessary to guide management actions that support ecosystems adapting to global change. 2. We analysed the independent and interactive effects of human impacts and natural drying on aquatic invertebrate communities—a key biotic group used to assess the health of European freshwaters. We calculated biological response metrics representing communities from 406 rivers in eight European countries: taxonomic richness, functional richness and redundancy, and biomonitoring indices that indicate ecological status. We analysed metrics based on the whole community and on a group of taxa with traits promoting resistance and/or resilience (‘high RR’) to drying. We also examined how responses vary across Europe in relation to climatic aridity. 3. Most community metrics decreased independently in response to impacts and drying. A richness-independent biomonitoring index (the average score per taxon; ASPT) showed particular potential for use in biomonitoring, and should be considered alongside new metrics representing high RR diversity, to promote accurate assessment of ecological status. 4. High RR taxonomic richness responded only to impacts, not drying. However, these predictors explained little variance in richness and other high RR metrics, potentially due to low taxonomic richness. Metric responsiveness could thus be enhanced by developing region-specific high RR groups comprising sufficient taxa with sufficiently variable impact sensitivities to indicate ecological status. 5. Synthesis and applications. Metrics are needed to assess the ecological status of dynamic river ecosystems—including those that sometimes dry—and thus to identify priority sites requiring action to tackle the causes of environmental degradation. Our results inform recommendations guiding the development of such metrics. We propose concurrent use of richness-independent ‘average score per taxon’ indices and metrics that characterize the richness of resistant and resilient taxa. We observed interactions between aridity, impacts and drying, highlighting that these new metrics should be region specific, river type specific and adaptable, promoting their ability to inform management actions that protect biodiversity in river ecosystems responding to climate change. European Cooperation in Science and Technology. Grant Number: CA15113

A checklist of water scavenger beetles from Morocco and their distribution in the country and North Africa is presented. It is based on (1) an exhaustive review of the literature (time span: 1914–2018); (2) more than 3150 individuals collected during extensive campaigns (2003–2018); and (3) an intensive revision of private collections. We found 52 species belonging to 14 genera and five subfamilies. Paracymus relaxus Rey, 1884 is reported for the first time from Morocco. Four species were excluded from the country’s fauna. A chorological analysis showed that most species found are essentially Mediterranean (48%) and Palaearctic (31%) elements. The subcosmopolitan elements and those whose distribution extends beyond the Palaearctic Region, in the Nearctic or Afrotropical Region, are less represented (21%). Most endemics are halophiles, pointing to the importance of the conservation of saline ecosystems.

The study was supported by the COST Action CA15113 Science and Management of Intermittent Rivers and Ephemeral Streams (http://www.smires.eu), funded by COST (European Cooperation in Science and Technology). NC was supported by the French research program Make Our Planet Great Again. MC-A was supported by the MECODISPER project (CTM2017-89295-P) funded by the Spanish Ministerio de Economia, Industria y Competitividad (MINECO) - Agencia Estatal de Investigacion (AEI) and cofunded by the European Regional Development Fund (ERDF). AC-R acknowledges funding by MINECO-AEI-ERDF (CGL2014-53140-P). CG-C was supported by the EDRF (COMPETE2020 and PT2020) and the Portuguese Foundation for Science and Technology, through the CBMA strategic program UID/BIA/04050/2019 (POCI-01-0145-FEDER-007569) and the STREAMECO project (Biodiversity and ecosystem functioning under climate change: from the gene to the stream, PTDC/CTA-AMB/31245/2017). JH was supported by the project 'Global taxonomic, functional and phylogenetic diversity of stream macroinvertebrate communities: unravelling spatial trends, ecological determinants and anthropogenic threats' funded by the Academy of Finland. PP and MP were supported by the Czech Science Foundation (P505-20-17305S). ZC was supported by the projects EFOP-3.6.1.-16-2016-00004, 20765-3/2018/FEKUTSTRAT and TUDFO/47138/2019-ITM. We thank two anonymous reviewers for insightful feedback that improved an earlier draft of this manuscript., Dispersal is an essential process in population and community dynamics, but is difficult to measure in the field. In freshwater ecosystems, information on biological traits related to organisms’ morphology, life history and behaviour provides useful dispersal proxies, but information remains scattered or unpublished for many taxa. We compiled information on multiple dispersal-related biological traits of European aquatic macroinvertebrates in a unique resource, the DISPERSE database. DISPERSE includes nine dispersal-related traits subdivided into 39 trait categories for 480 taxa, including Annelida, Mollusca, Platyhelminthes, and Arthropoda such as Crustacea and Insecta, generally at the genus level. Information within DISPERSE can be used to address fundamental research questions in metapopulation ecology, metacommunity ecology, macroecology and evolutionary ecology. Information on dispersal proxies can be applied to improve predictions of ecological responses to global change, and to inform improvements to biomonitoring, conservation and management strategies. The diverse sources used in DISPERSE complement existing trait databases by providing new information on dispersal traits, most of which would not otherwise be accessible to the scientific community., COST Action Science and Management of Intermittent Rivers and Ephemeral Streams - COST (European Cooperation in Science and Technology) CA15113, French research program Make Our Planet Great Again, MECODISPER project - Spanish Ministerio de Economia, Industria y Competitividad (MINECO) - Agencia Estatal de Investigacion (AEI) CTM2017-89295-P, European Union (EU), MINECO-AEI-ERDF CGL2014-53140-P, EDRF (COMPETE2020), Portuguese Foundation for Science and Technology, through the CBMA strategic program UID/BIA/04050/2019 (POCI-01-0145-FEDER-007569), STREAMECO project (Biodiversity and ecosystem functioning under climate change: from the gene to the stream) PTDC/CTA-AMB/31245/2017, project 'Global taxonomic, functional and phylogenetic diversity of stream macroinvertebrate communities: unravelling spatial trends, ecological determinants and anthropogenic threats' - Academy of Finland, Grant Agency of the Czech Republic P505-20-17305S, EDRF (PT2020), EFOP-3.6.1.-16-2016-00004, 20765-3/2018/FEKUTSTRAT, TUDFO/47138/2019-ITM

Motivation Dispersal is an essential process in population and community dynamics but is difficult to measure in the field. In freshwater systems, relevant information on the dispersal of many taxa remains scattered or unpublished, and biological traits related to organisms’ morphology, life history and behaviour offer useful dispersal proxies. We compiled information on selected dispersal-related biological traits of European aquatic macroinvertebrates in a unique source: the DISPERSE database. Information within DISPERSE can be used to address fundamental questions in metapopulation ecology, metacommunity ecology, macroecology, and eco-evolutionary research. From an applied perspective, the consideration of dispersal proxies can also improve predictions of ecological responses to global change, and contribute to more effective biomonitoring and conservation management strategies. Main types of variable contained Selected macroinvertebrate dispersal-related biological traits: maximum body size, adult female wing length, adult wing pair type, adult life span, number of reproductive cycles per year, lifelong fecundity, dispersal mode (i.e. active, passive, aquatic, aerial), and propensity to drift. Spatial location Europe. Time period Taxa considered are extant with recent records. Most data were collected in the 20th century and in the period 2000-2019. Major taxa and level of measurement Aquatic macroinvertebrates from riverine and lacustrine ecosystems, including Mollusca, Annelida, Platyhelminthes, and Arthropoda such as Crustacea and Insecta. For Insecta, aquatic stages and the aerial (i.e. flying) phases of adults were considered separately. Genus-level taxonomic resolution used, except for some Annelida and Diptera, which are coded at the sub-class, family or sub-family level. In total, the database includes 39 trait categories grouped into nine dispersal-related traits for 480 taxa. Software format The data file is in Excel workbook. BIOSKETCH Many of the authors are members of the European Cooperation in Science and Technology (COST) Action CA15113 Science and Management of Intermittent Rivers and Ephemeral Streams (SMIRES, www.smires.eu ), which aims to improve our understanding of intermittent rivers and ephemeral streams (IRES) and translate this into science-based, sustainable management of river networks. One of the main goals of SMIRES is to facilitate sharing of data and experience, bringing together researchers from many disciplines and stakeholders and creating synergies through networking. The dataset provided and analyzed herein reflects networking and collaboration within the SMIRES working group dedicated to Community Ecology and Biomonitoring.

We describe four species of Ochthebius subgenus Cobalius (Coleoptera, Hydraenidae) from coastal rockpools of the western Palaearctic Region: O. anzar sp. nov. (south Morocco, plus a possible specimen from Lanzarote, Canary Islands), O. cortomaltese sp. nov. (Malta), O. evae sp. nov. (Atlantic coast of Morocco and Mediterranean coast of south Spain), and O. gorgadensis sp. nov. (Ilha de Santiago, Cabo Verde). A molecular phylogeny of all described species of Cobalius recovered three clades: (1) O. serratus Rosenhauer, 1864 as sister to the newly defined O. algicola group, including most of the Macaronesian species of Cobalius (O. algicola Wollaston, 1871 from Madeira, O. freyi d’Orchymont, 1941 from Azores, O. lanthanus Ribera and Foster 2018 from Gran Canaria and Lanzarote, and O. balfourbrownei Jäch, 1989 and O. gorgadensis sp. nov. from Cabo Verde); (2) O. anzar sp. nov. as sister to the species of the newly defined O. biltoni group (O. biltoni Jäch and Delgado, 2017 from Sicily, plus O. evae sp. nov. and O. cortomaltese sp. nov.); and (3) the newly defined O. lejolisii group, including O. lejolisii Mulsant and Rey, 1861 (Atlantic coast from south Morocco to the British Islands) plus O. subinteger Mulsant and Rey, 1861 (western Mediterranean), O. adriaticus Reitter, 1886 and its subspecies, O. celatus Jäch, 1989 and O. asper Sahlberg, 1900 stat. rev., previously considered a synonym of O. subinteger (all from the Central and Eastern Mediterranean). We note the strong intrapopulational morphological variation and the contrasting lack of consistent diagnostic characters between populations, despite the deep genetic divergence between lineages found within some species. We also discuss the widespread evolutionary convergence in beetles living in coastal habitats, sometimes in different genera or even families., This study was partly funded by projects CGL2013-48950-C2-1&2-P (AEI/FEDER, UE) to IR and AM and CGL2017-84157-P (AEI/FEDER, UE) to J Velasco.

One of the main challenges in ecology, biogeography and evolution is to understand and predict how species may respond to environmental changes. Here we focus on the deep subterranean environment, a system that minimizes most of the typical uncertainties of studies on epigean (surface) environments. Caves are relatively homogeneous habitats with nearly constant environmental conditions and simplified biological communities, allowing to control for biotic interactions. Thus, this particular system could be considered a natural habitat whose environmental conditions are similar to what can be reproduced in a laboratory, being an ideal model system for ecological, biogeographical and evolutionary studies. Subterranean species may potentially be used to assess the capability to persist in situ in a global change scenario, as they cannot accommodate to drastic changing conditions by behavioural plasticity, microhabitat use or by migrating to distant, more suitable areas, something frequent in epigean environments. In order to provide accurate predictions of the response of the subterranean biodiversity to climate change, we encourage evolutionary biologist, biogeographers and conservation biologist to work in this interesting ecosystem., DS-F was supported by a post-doctoral contract funded by Universidad de Castilla-La Mancha and the European Social Fund (ESF). This work was partly funded by two projects funded by the Spanish Ministry of Economy and Competitiveness (CGL2016-76995-P to DSF and CGL2016-76705-P to IR).

Ongoing climate change is driving dramatic range shifts in diverse taxa worldwide, and species responses to global change are likely to be determined largely by population responses at geographical range margins. Here we investigate the metabolic and reproductive plasticity in response to water temperature and salinity variation of two populations of the eurythermic saline water bug Sigara selecta: one population located close to the northern edge of its distribution, in a relatively cold, thermally stable region (SE England - 'marginal'), and one close to the range centre, in a warmer and more thermally variable Mediterranean climate (SE Spain - 'core'). We compared metabolic and oviposition rates and egg size, following exposure to one of four different combinations of temperature (15 and 25°C) and salinity (10 and 35gL-1). Oviposition rate was significantly higher in the marginal population, although eggs laid were smaller overall. No significant differences in oxygen consumption rates were found between core and marginal populations, although the marginal population showed higher levels of plasticity in both metabolic and reproductive traits. Our results suggest that population-specific responses to environmental change are complex and may be mediated by differences in phenotypic plasticity. In S. selecta, the higher plasticity of the marginal population may facilitate both its persistence in current habitats and northward expansion with future climatic warming. The less plastic core population may be able to buffer current environmental variability with minor changes in metabolism and fecundity, but could be prone to extinction if temperature and salinity changes exceed physiological tolerance limits in the future.

Made available in DSpace on 2020-12-12T00:56:40Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-04-01 Introduction: The clinical longevity of tooth restoration -whether directly or indirectly using composites- greatly depends on the quality and stability of the marginal adaptation. Even today, dental restoration failure is a major complication in everyday dental practice. Objective: To evaluate the effect of restoration techniques on the microtensile bond strength and marginal integrity of class II cavities. Methods: An experimental in vitro investigation was made. Preparations (5 × 4 × 2 mm) below the cement-enamel junction were performed in 45 human maxillary premolars (n= 15) that were the sample of the study selected to random. The G1 group incrementally received Spectrum TPH3 Dentsply De trey in three horizontal incremental layers. The G2 group received a bulk restoration technique (one 4-mm increment of Surefill SDR flow plus one 1-mm horizontal capping layer of Spectrum TPH3 Dentsply De trey using a metal matrix band. For the G3 group, impressions were made from each cavity preparation, and Spectrum was used to complete an indirect composite restoration. After storage (24 h/37 °C), the proximal surfaces of each tooth were polished with Sof-Lex disks. For microtensile bond strength testing, all premolars were sectioned into resin-dentine beams (0.8 mm2) and were tested under tension (0.5 mm/min). Results: Microtensile bond strength testing and marginal integrity values were not statistically significantly affected by the type of restoration technique used (p> 0.05). Conclusions: The SurefillSDR flow that used a capping layer made of conventional composite can be an alternative to reduce procedure durations as well as additional steps in the restorative technique. University of Cuiaba-UNIC School of Dentistry Department of Restorative Dentistry CEUMA University Dentistry Masters Program Department Ponta Grossa State University School of Dentistry Department of Restorative Dentistry São Paulo State University - Unesp School of Dentistry/Unesp Restorative Dentistry Department University of Chile Institute of Biomedical Sciences-Autonomous University of Chile Medical University of La Habana Medical Faculty “Victoria de Girón” Department of Dentistry Universidad Politécnica y Artística del Paraguay. São Paulo State University - Unesp School of Dentistry/Unesp

Naturally stressed ecosystems hold a unique fraction of biodiversity. However, they have been largely ignored in biomonitoring and conservation programmes, such as the EU Water Framework Directive, while global change pressures are threatening their singular values. Here we present a framework to classify and evaluate the ecological quality of naturally stressed rivers along a water salinity gradient. We gathered datasets, including aquatic macroinvertebrate assemblages and environmental information, for 243 river locations across the western Mediterranean to: a) gauge the role of natural stressors (salinity) in driving aquatic community richness and composition; b) make river classifications by encompassing the wide range of environmental and biological variation exhibited by Mediterranean rivers; c) provide effective biomonitoring metrics of ecological quality for saline rivers. Our results showed that water salinity played a pivotal role in explaining the community richness and compositional changes in rivers, even when considering other key and commonly used descriptors, such as elevation, climate or lithology. Both environmental and biologically-based classifications included seven river types: three types of freshwater perennial rivers, one freshwater intermittent river type and three new saline river types. These new saline types were not included in previous classifications. Their validation by independent datasets showed that the saline and freshwater river types represented differentiable macroinvertebrate assemblages at family and species levels. Biomonitoring metrics based on the abundance of indicator taxa of each saline river type provided a much better assessment of the ecological quality of saline rivers than other widely used biological metrics and indices. Here we demonstrate that considering natural stressors, such as water salinity, is essential to design effective and accurate biomonitoring programmes for rivers and to preserve their unique biodiversity., CG-C and PA are supported by “Juan de la Cierva-Formación” research contracts (funded by the Ministry of Economy and Competitiveness - MINECO, Spain, FJCI-2015-25785 and FJCI-2014-20581, respectively). Saline river surveys were funded by the Ministry of Science and Innovation (Spain) through R&D&I Projects BOS2002-00702 (JV) and CGL2006-04159/BOS (AM).

Running waters in Mediterranean regions are strongly regulated by dams, which produce significant alterations to natural flow regimes. Climate change will reduce discharge and increase flow intermittence in Mediterranean streams, which will lead to an intensified flow regulation to meet water demands. Very little is known about how the functional features of aquatic communities vary along combined anthropogenic flow alteration and natural intermittence gradients. As intermittent streams are subjected to natural stress (droughts and flash floods), the flow regime alteration effect may differ from that observed in perennial rivers. Consequently, studies that aim to determine the effects of flow regulation on the functioning of aquatic communities in a global change context are crucial. By applying linear mixed‐effect models and null models to the macroinvertebrate communities from 65 stream sites in the Segura River Basin (south‐east Spain), we assessed the separate effects of natural flow intermittence and flow regulation, as well as their interaction, on biological traits and functional diversity indices. Natural flow intermittence and flow regulation were mainly associated with loss of taxa with semivoltine or univoltine cycles and more sensitive aquatic stages (i.e. eggs), and with the replacement by taxa with multivoltine cycles and more resistant aquatic stages (i.e. adults). Flow regulation intensified the impact of natural flow intermittence on some biological traits, producing synergistic effects (i.e. decreasing interstitial taxa and tegument breathers and increasing taxa with aquatic adult stages). At the same time, antagonistic (life cycle) and opposing (shredders) interaction effects were also observed. Functional diversity, functional dispersion, and functional redundancy underwent a non‐random decrease as the flow regime alteration increased, and a significant antagonistic interaction was also found between both stressors for functional redundancy. In general, flow regulation effects were stronger in perennial than in intermittent streams because natural intermittence imposes a previous eco‐evolutionary pressure on aquatic biota by selecting those resistant or recovery traits that confer resilience to anthropogenic flow regime alterations. Thus, the natural flow regime influences the functional sensibility of communities to anthropogenic flow alteration. info:eu-repo/semantics/acceptedVersion

Melloulou River, which is located in Middle Atlas of Morocco, is a good example of a very wet and poorly known basin, and therefore of special conservation concern. The aim of this study was to draw up an initial inventory of the benthic macroinvertebrates taxa, and to analyze its longitudinal distribution in the basin, particularly searching for the main abiotic factors addressing its zonation for improving future management and conservation actions. The study allowed identifying 161 taxa belonging to 127 genera and 80 families, most new records for northeast Morocco. The biotypology, which was studied by using Foucart' Factorial Correspondence Analysis (FCA), Partial Triadic analysis (PTA), and IndVal showed a longitudinal distribution of macroinvertebrates mainly governed by altitude, slope and current velocity. The studied biota revealed the presence of three assemblages and an important number of ubiquitous species not included in any group. The first group is located in the upper courses of Melloulou River representing a community proper of a crenon-rhithron zone; the second occurs in the middle and lower courses, and clearly reflects the community of a large potamon; the third one is a mixture of taxa capable to colonize the entire study area. Our finding, highlight the singular aquatic biodiversity occurring in the Melloulou River and its extraordinary changing water dynamic over time, which are key factors for future monitoring, as well as managing and conservation actions.

Considering how organisms adapt to stress is essential if we are to anticipate biological responses to global change in ecosystems. Communities in stressful environments can potentially be assembled by specialists (i.e. species that only occur in a limited range of environmental conditions) and/or generalist species with wider environmental tolerances. We review the existing literature on the salinity tolerance of aquatic insects previously identified as saline specialists because they were exclusively found in saline habitats, and explore if these saline realized niche specialists are also specialists in their fundamental niches or on the contrary are fundamental niche generalist species confined to the highest salinities they can tolerate. The results suggest that species inhabiting saline waters are generalists in their fundamental niches, with a predominant pattern of high survival in freshwater-low salinity conditions, where their fitness tends to be similar or even higher than in saline waters. Additionally, their performance in freshwater tends to be similar to related strictly freshwater species, so no apparent trade-off of generalization is shown. These results are discussed in the framework of the ecological and evolutionary processes driving community assembly across the osmotic stress gradient, and their potential implications for predicting impacts from saline dilution and freshwater salinization. This article is part of the theme issue ‘Salt in freshwaters: causes, ecological consequences and future prospects’.

One of the main challenges in disciplines such as ecology, biogeography, conservation and evolutionary biology is to understand and predict how species will respond to environmental changes, especially within a climate change context. We focus on the deep subterranean environment to minimize uncertainties in predictions, because it is one of the few ecosystems in nature whose environmental conditions are as homogeneous as those in the laboratory and their species cannot accommodate to changing conditions by behavioural plasticity, dispersal or microhabitat use (i.e., their only possibility to cope with climate change is to persist in situ). The hypotheses established for this project are based on the exciting results obtained in some of our previous studies, in which, we found that different subterranean beetle species living under different environmental conditions have identical/similar narrow thermal tolerance ranges, suggesting a lack of evolutionary adjustment to ambient temperature for these species. This could be due to the loss of some of the physiological mechanisms related to thermal tolerance, with a likely high metabolic cost, in a stable environment but with severe resource restrictions. However, the question that remains is to what extent this surprising narrow and homogeneous thermal niche is common for the whole subterranean biodiversity, and how this issue could determine the fate of subterranean biodiversity to climate change. In this project, we are testing for the generality of these exciting previous findings by studying the thermal niche (species acclimation abilities and thermal tolerances) of different lineages of cave beetles with different degrees of specialization to subterranean environments and from different geographical areas (Pyrenees and Cantabrian Mountains) (Suppl. material 1).

Thermal tolerance is a key vulnerability factor for species that cannot cope with changing conditions by behavioural adjustments or dispersal, such as subterranean species. Previous studies of thermal tolerance in cave beetles suggest that these species may have lost some of the thermoregulatory mechanisms common in temperate insects, and appear to have a very limited thermal acclimation ability. However, it might be expected that both thermal tolerance and acclimation ability should be related with the degree of specialization to deep subterranean environments, being more limited in highly specialized species. To test this hypothesis, we use an experimental approach to determine the acclimation capacity of cave beetles within the tribe Leptodirini (family Leiodidae) with different degrees of specialization to the deep subterranean environment. For this, we acclimate groups of individuals at a temperature close to their upper thermal limit (20ºC) or a control temperature (approximately that of the cave in which they were found) for 2 or 10 days (short- vs. long-term acclimation). a temperature close to their upper thermal limit (20ºC) or a control temperature (approximately that of the cave in which they were found) for 2 or 10 days (short- vs. long-term acclimation). Upper thermal limits (heat coma temperature, HC) are then measured for each individual using a ramping protocol (rate of increase of 1ºC/min) combined with infrared thermography and video recording. Preliminary results in a deep subterranean species (Speonomidius crotchi, with an intermediate degree of specialization) showed no significant effect of acclimation temperature in HC at any of the exposure times. Such reduced thermal plasticity could be also expected for other highly specialized subterranean species. The potential implications of these findings for subterranean biodiversity in a climate change context are discussed.

Entanglement is at the core of quantum physics and so, one may conjecture that it should have some influence on atomic and molecular response properties. The usual way of treating entanglement is by applying information theory via the von Newman entropy. Given that the principal propagator is the operator that contains the physical information that arises due to the transmission of the effects of two external perturbations through the electronic framework of a quantum system, it should have in it the information necessary to quantify the likely entanglement among molecular orbital excitations. In this article we first propose a proper density matrix and from it, the way to quantify entangled excitations by using information theory. The NMR J-couplings are among the best candidates to learn about the potentialities of this formalism. We applied this new tool to analyze the famous Karplus rule and found a relationship between the dihedral angular dependence and the entanglement. We also found that the entangled excitations are related to electron correlation. The new formalism can be applied to all other response properties. Fil: Millán, Leonardo Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Modelado e Innovación Tecnológica. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas Naturales y Agrimensura. Instituto de Modelado e Innovación Tecnológica; Argentina Fil: Giribet, Claudia Gloria. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentina Fil: Aucar, Gustavo Adolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Modelado e Innovación Tecnológica. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas Naturales y Agrimensura. Instituto de Modelado e Innovación Tecnológica; Argentina

New faunistic and distributional data on aquatic Hemiptera from the Oriental Region of Morocco and the Moulouya River basin, covering an area of 119,268 km2, are presented. An annotated list of 45 species, 21 genera and 11 families is provided. Nine species are new records for the entire studied area, and two for the Moulouya River basin. We rediscovered Velia noualhieri iberica and Notonecta viridis after eight decades. We also provide novel records for Aphelocheirus pemae and Hebrus atlas, which were recently described from Morocco, and for the invasive corixid Trichocorixa verticalis verticalis. The dominance of species with broad distributions points to the high dispersal dynamics of the Hemiptera community in the study area, similar to that of other areas where a semiarid climate prevails.

Biodiversity databases are typically incomplete and biased. We identify their three main limitations for characterizing the geographic distributions of species: unknown levels of survey effort, unknown absences of a species from a region, and unknown level of repeated occurrence of a species in different samples collected at the same location. These limitations hinder our ability to distinguish between the actual absence of a species at a given location and its (erroneous) apparent absence as consequence of inadequate surveys. Good practice in biodiversity research requires knowledge of the number, location and degree of completeness of relatively well-surveyed inventories within territorial units. We herein present KnowBR, an application designed to simultaneously estimate the completeness of species inventories across an unlimited number of spatial units and different geographical extents, resolutions and unit expanses from any biodiversity database. We use the number of database records gathered in a territorial unit as a surrogate of survey effort, assuming that such number correlates positively with the probability of recording a species within such area. Consequently, KnowBR uses a “record-by-species” matrix to estimate the relationship between the accumulated number of species and the number of database records to characterize the degree of completeness of the surveys. The final slope of the species accumulation curves and completeness percentages are used to discriminate and map well-surveyed territorial units according to user criteria. The capacity and possibilities of KnowBR are demonstrated through two examples derived from data of varying geographic extent and numbers of records. Further, we identify the main advances that would improve the current functionality of KnowBR., The development of KnowBR has been supported by the projects BIOWEB (CGL2011-15622-E BOS) and BANDENCO (POII11-0277-5747) founded by Spanish Ministerio de Ciencia e Innovación and the Consejería de Educación, Ciencia y Cultura-Junta de Comunidades de Castilla-La Mancha, respectively. DSF was supported by a post-doctoral contract funded by Universidad de Castilla-La Mancha and the European Social Fund (ESF).

International audience; Some species of the diving beetle tribe Hygrotini (subfamily Hydroporinae) are among the few insects able to tolerate saline concentrations more than twice that of seawater. However, the phylogenetic relationships of the species of Hygrotini, and the origin and evolution of tolerance to salinity in this lineage, are unknown. In this work, we aim to reconstruct how many times salinity tolerance did evolve in Hygrotini, whether this evolution was gradual or if tolerance to hypersalinity could evolve directly from strictly freshwater (FW) species, and to estimate the probabilities of transition between habitats. We build a phylogeny with ca. 45% of the 137 species of Hygrotini, including all major lineages and almost all of the known halo-phile or tolerant species. We used sequence data of four mitochondrial (COI-5′, COI-3′, 16S + tRNA and NADH1) and three nuclear (28S, 18S and H3) gene fragments, plus ecological data to reconstruct the history of the salinity tolerance using Bayesian inference. Our results demonstrate multiple origins of the tolerance to salinity, although most saline and hypersaline species were concentrated in two lineages. The evolution of salinity was gradual, with no direct transitions from FW to hypersaline habitats, but with some reversals from tolerant to FW species. The oldest transition to saline tolerance, at the base of the clade with the highest number of saline species, was dated in the late Eocene-early Oligocene, a period with decreasing temperature and precipitation. This temporal coincidence suggests a link between increased aridity and the development of tolerance to saline waters, in agreement with recent research in other groups of aquatic Coleoptera.

Distribució d’escarabats aquàtics de l’est del Marroc (Coleoptera, Polyphaga) Es presenten antigues i noves dades faunístiques i de distribució de Polyphaga (Coleoptera) aquàtics de l’est del Marroc, incloent–hi la regió oriental i la conca del riu Moulouya. S’aporta una llista de 91 espècies pertanyents a 27 gèneres i set famílies. Ochthebius quadrifossulatus (Hydraenidae) i Pomatinus substriatus (Dryopidae) són nous registres a la conca del riu Moulouya i Helophorus occidentalis, H. discrepans, H. flavipes, Hydrochus flavipes, Anacena globulus, Enochrus fuscipennis i Hydrobius fuscipes, tots pertanyents a la família Hydrophilidae, i Limnebius furcatus, Ochthebius aeneus i O. merinidicus (tots Hydreanidae) són nous a tota l’àrea estudiada de l’est del Marroc. Vam trobar un clar predomini d’elements paleàrtics, principalment mediterranis, amb una proporció elevada d’endemismes iberomagribins. Aquest patró corotípic és similar als observats en altres ordres de macroinvertebrats a la mateixa àrea d’estudi. Dades publicades a GBIF (doi: 10.15470/saajc8), Distribution of aquatic beetles from the east of Morocco (Coleoptera, Polyphaga) We present old and new faunistic and distributional data on aquatic Polyphaga (Coleoptera) from the east of Morocco, comprising the Oriental Region and the basin of Moulouya River. A checklist of 91 species belonging to 27 genera and seven families is provided. Ochthebius quadrifossulatus (Hydraenidae) and Pomatinus substriatus (Dryopidae) are new records for the basin of Moulouya River, and Helophorus occidentalis, H. discrepans, H. flavipes, Hydrochus flavipes, Anacena globulus, Enochrus fuscipennis and Hydrobius fuscipes, all belonging to the family Hydrophilidae, and Limnebius furcatus, Ochthebius aeneus and O. merinidicus (all Hydreanidae) are new for the entire studied area of Eastern Morocco. We found a clear dominance of the Palearctic elements, mainly Mediterranean, with a high proportion of Ibero–Maghrebian endemisms. This chorotype pattern is similar to those observed for other macroinvertebrates orders in the same study area. Data published in GBIF (doi: 10.15470/saajc8), Distribución de escarabajos acuáticos del este de Marruecos (Coleoptera, Polyphaga) Se presentan antiguos y nuevos datos faunísticos y de distribución de Polyphaga (Coleoptera) acuáticos del este de Marruecos, incluidas la región oriental y la cuenca del río Moulouya. Se aporta un listado de 91 especies pertenecientes a 27 géneros y siete familias. Ochthebius quadrifossulatus (Hydraenidae) y Pomatinus substriatus (Dryopidae) constituyen nuevos registros en la cuenca del río Moulouya y Helophorus occidentalis, H. discrepans, H. flavipes, Hydrochus flavipes, Anacena globulus, Enochrus fuscipennis e Hydrobius fuscipes, pertenecientes todos ellos a la familia Hydrophilidae, y Limnebius furcatus, Ochthebius aeneus y O. merinidicus (todos ellos Hydreanidae) son nuevos en la totalidad del área estudiada del este de Marruecos. Encontramos un claro predominio de elementos paleárticos, principalmente mediterráneos, con una elevada proporción de endemismos ibero–magrebíes. Este patrón corotípico es similar a los observados en otros órdenes de macroinvertebrados en la misma área de estudio. Datos publicados en GBIF (doi: 10.15470/saajc8)

Abiotic stress shapes how communities assemble and support ecological functions. However, it remains unclear whether artificially increasing or decreasing stress levels would lead to communities assembling predictably along a single axis of variation or along multiple context-dependent trajectories of change. In response to stress intensity alterations, we hypothesize that a single trajectory of change occurs when trait-based assembly prevails, while multiple trajectories of change arise when dispersal-related processes modify colonization and trait-filtering dynamics. Here, we tested these hypotheses using aquatic macroinvertebrates from rivers exposed to gradients of natural salinity and artificially diluted or salinized ion contents. Our results showed that trait-filtering was important in driving community assembly in natural and diluted rivers, while dispersal-related processes seemed to play a relevant role in response to salinization. Salinized rivers showed novel communities with different trait composition, while natural and diluted communities exhibited similar taxonomic and trait compositional patterns along the conductivity gradient. Our findings suggest that the artificial modification of chemical stressors can result in different biological communities, depending on the direction of the change (salinization or dilution), with trait-filtering, and organism dispersal and colonization dynamics having differential roles in community assembly. The approach presented here provides both empirical and conceptual insights that can help in anticipating the ecological effects of global change, especially for those stressors with both natural and anthropogenic origins.This article is part of the theme issue ‘Salt in freshwaters: causes, ecological consequences and future prospects’.