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The Caucasus and adjacent areas are inhabited by fifteen species of mayflies of the genus Epeorus, subgenus Caucasiron Kluge, 1997 (Heptageniidae). This identification guide aims to facilitate an accurate species identification of their larvae and sum up all available information on their taxonomy and distribution. An identification key is provided, and the important diagnostic characters of all species are described and illustrated. The larva of E. (C.) insularis (Braasch, 1983) is described for the first time. This study enables the routine identification of Caucasiron larvae necessary for biomonitoring and hydrobiological research in the Caucasus region.

Warming and predation risk are ubiquitous environmental factors that can modify life histories and population dynamics of aquatic ectotherms. While separate responses to each of these factors are well understood, their joint effects on individual life histories and population dynamics remain largely unexplored. Current theory predicts that the magnitude of prey behavioural, physiological, and life history responses to predation risk should diminish with warming due to the reduced metabolic scope. However, empirical support for this prediction remains equivocal, and experiments covering a substantial proportion of individual prey ontogeny until maturation are lacking. To fill these gaps, we ran a laboratory experiment to investigate how warming and non-consumptive predation risk influence life history responses in the larvae of the mayflyCloeon dipterum, an aquatic insect with highly plastic development. We reared larvae of varying initial sizes at three temperatures (21, 24, and 27 degrees C) in a risk-free environment and under predation risk signalled by chemical cues from dragonfly larvae (Aeshna cyanea), and followed their individual survival, growth, and development until emergence. SomeC. dipterumlarvae substantially prolonged their development and the proportion of theseslowindividuals declined rapidly with temperature and increased with predation risk. We attribute this response to cohort splitting, a common life history strategy of aquatic insects and other taxa in unpredictable environment. Growth, development, and maturation varied predictably with temperature in thefastlarvae that did not prolong their development. They grew and developed faster but matured at smaller sizes with increasing temperature. Predation risk tended to slow down individual growth and development in line with the reduced metabolic scope hypothesis, but the differences were relatively minor and observable only at 21 degrees C. Survival to subimago increased with predation risk, possibly due to indirect effects mediated by dissolved micronutrients, but did not vary significantly with temperature. Survival also tended to be higher in theslowindividuals. This partly compensated for a smaller final size relative to thefastindividuals and made both strategies comparable in overall fitness. Our results show that warming may erode individual-level variability in life history responses to predation risk. This implies that warming can synchronise population dynamics and consequently make such populations more vulnerable to unpredictable disturbances.

Despite the fact that native species of amphipods have been recognized as active predators similarly to invasive species, little is known about their predatory impact on aquatic communities. In this study, we used a laboratory experiment, a field enclosure experiment, and an analysis of natural community data to demonstrate how Gammarus fossarum affects the species composition of benthic communities by imposing survival selection on its prey. Our laboratory single-prey experiment brought a clear evidence that tube-less chironomids are vulnerable prey and that the predation rate on the tube-dwelling chironomids decreases with increasing tube toughness (from the soft tubes made of detritus to the hard tubes made of sand or calcium carbonate grains). We found that the introduction of G. fossarum to field enclosures significantly changed the species composition of a macroinvertebrate community at an experimental spring fen site. The soft-bodied, slow moving, and tube-less taxa were depleted the most. It appears that the observed patterns were a result of predator’s preference rather than encounter rate. Survival selection was detected also in natural communities across a large spatial scale. In accordance with the experiments, high densities of G. fossarum limited the proportion or abundance of vulnerable prey. Our study (1) provides the first convincing evidence that biotic interactions have a structuring effect on the spring fen communities, (2) documents how the predatory effect in a community depends on an interplay between the prey handling behaviour of the predator and species-specific susceptibility of prey, and (3) shows that an omnivorous native amphipod may have a strong impact on aquatic communities despite it is regarded less aggressive than its invasive relatives.

Groundwater dependent ecosystems are recognized as biodiversity hotspots, being,apart many negative human impacts, highly threatened also by ongoing climate warming. Clitellata (Annelida) are dominant invertebrates of permanent fauna in spring habitats, representing a heterogeneous group including both specialized cold stenothermic and ubiquitous eurythermic species. Therefore, they seem to be a good model group to compare the effects of local spring water temperature (recorded in situ by data loggers) and mesoclimate (i.e., local) air temperature. By the analysis of clitellate assemblages at 41 isolated Western Carpathian spring fens, we found that their species composition was significantly driven by mesoclimate air temperature and springwater temperature independently of other important environmentalvariables (i.e., water mineralization, oxygen content, and total organic carbon). Theeffect of various environment related and temperature related variables on thenumber of clitellate species was analyzed separately for two categories, that is,substrate dwellers (endobenthic species) and surface active (epibenthic) species. The decrease of the number of species with the increasing amount of inorganic particles in substrate was observed in the substrate dwellers. Mesoclimate air temperature had no significant effect on the number of species of substrate dwellers.However, water temperature, specifically its daily fluctuation, turned out to have a strong effect. Only the sites with no or moderate fluctuation were inhabited by cold stenotherm spring specialists and cold water species. In contrast, no significant response to any temperature parameter was found for the number of surface active species, which was driven only by other environmental variables. Our results suggest that climatically induced increase in temperature fluctuation of spring waters can result in notable reduction of cold adapted clitellate species (mainly the family Lumbriculidae) at the expense of eurythermic species. Such a scenario predicts compositional changes leading to clitellate assemblages with a dominance ofgeneralist and semiaquatic species.

Surface coal mining severely affects natural ecosystems, though it might also result in an establishment of biologically unique anthropogenic habitats. We studied spontaneously created post-mining calcareous brooks located at the brown coal spoil heap in the Sokolov coal basin (Czechia). Despite their extreme water conditions, linked most to the ionic mixture of dissolved ions (mainly SO 4 2− , Ca 2+ and Mg 2+ ), and ferric hydroxide precipitations, we recorded unexpectedly species-rich assemblages there (150 species), including several spring fen specialists (31 species) and eight threatened red-listed species. Macroinvertebrate assemblages of post-mining calcareous habitats were compared with those reported from natural brooks draining Western Carpathians calcareous spring fens. The species richness found in the post-mining calcareous brooks was significantly lower than that of the natural calcareous spring brooks. Although we found 29% of species recorded in the two study systems in common (i.e. 80 species), species composition of their assemblages was systematically distinct. This suggests a possible role of environmental filtering in the post-mining brooks and/or dispersal limitation of some species typical for natural calcareous spring brooks (e.g. Trichodrilus strandi , Bythinella austriaca ). In contrast, many macroinvertebrates, particularly those of high dispersal capacities (i.e. Odonata, Coleoptera and Diptera), can recognize post-mining calcareous brooks as surrogate habitats for the natural calcareous spring brooks.

Recent studies on diversity of stream amphipods proposed that the Western Carpathians have served as an important glacial refugium of freshwater fauna. If this scenario is true, a considerably high molecular diversity can be expected in this biogeographic region also for other taxa. In our project, we aimed to uncover and characterize molecular diversity of benthic macroinvertebrate fauna of spring fens, a well studied and hence convenient model community. Using a DNA metabarcoding approach, we sequenced a fragment of the COI gene of pooled spring fen invertebrate communities from 21 localities in the Western Carpathians. The preliminary analysis of the sequences revealed a substantially higher amount of operational taxonomic units (OTUs), when compared to the number of taxa identified in the same spring fens based on morphological characters. The lack of reference sequences in public databases (Barcoding of Life Database, GenBank) for the majority of the detected OTUs indicates that the Western Carpathian region is not yet sufficiently covered by barcoding efforts, and suggests that there indeed may be a considerable unrecognized diversity of macrozoobenthos. However, most newly uncovered diversity is concentrated in a few taxa such as the dipteran families Tabanidae and Ceratopogonidae, annelid species (complexes) Eiseniella tetraedra and Helobdella stagnalis or the amphipod genus Gammarus. In the future, these findings will be the basis for several levels of research: detailed investigation of seemingly hyperdiverse taxa (phylogeography, phylogeny, reference coverage) and comparison of overall molecular diversity of these communities in the Western Carpathians and neighbouring Bohemian Massif, a region where we expect much lower diversity due to different biogeographic history.

Our understanding of functional roles of aquatic invertebrate taxa is still limited even for common species, although being crucial for explanations of patterns observed in natural communities. As only recently shown, the common native European amphipodGammarus fossarum, traditionally treated as a shredder of leaf litter, shows predatory behaviour which may influence the composition of invertebrate assemblages. However, the evidence for the predation effect ofG. fossarumon natural assemblages at the within-site scale is still lacking. Therefore, we collected 50 quantitative samples of macroinvertebrates along with the important environmental variables within a heterogeneous calcareous spring fen. Using linear regression, we explored the relationships between the abundance ofG. fossarum(separately adult and juvenile) and the abundance and number of taxa for two groups of invertebrates differing in their susceptibility to predation, (a) hard-bodied taxa with protective body structures, such as shells and calcified cuticles, and (b) soft-bodied taxa without those protections. We separated the effect ofG. fossarumfrom that of environmental conditions using variation partitioning. Our results showed that only the abundance of soft-bodied invertebrates was negatively correlated with the abundance of adultG. fossarum. However, the proportion of variation explained purely by predation (5.5%) was much lower than the one explained by the environment (33.8%). BothG. fossarumand soft-bodied invertebrates were positively associated with organic matter. Although hard-bodied invertebrates consisted of only a few taxa, they were more numerous than soft-bodied invertebrates, and only environmental control was confirmed for them. Despite the limitations of the used correlative approach, we conclude thatG. fossarumcan significantly control the abundance of vulnerable taxa in natural assemblages. Its predatory effects, however, may be relatively low and easily confounded by the effect of environmental control.

The present contribution gives a faunistic overview on the distribution of Caenidae in Iran. Four species have so far been reported, of which Caenis macrura Stephens, 1835 by far is the most abundant and most widely spread species. Caenis kopetdagi Kluge, 1985 was previously only known from three localities in the Kopet Dag Mountain range, which stretches along the border between Turkmenistan and Iran. We report this species from three further localities at the western border of the Zagros Mountains in southwest Iran, thus considerably expanding its distribution. The nymph of Caenis kopetdagi is re-described, its validity is confirmed, and modern diagnostic characters are added. Its CO1 sequence is provided and compared with sequences of other species of Caenis Stephens, 1835 occurring in the Middle East. The habitat of C. kopetdagi as well as the distribution of Caenidae in Iran and of Caenis in the Middle East is also discussed.

Combining morphological and molecular data in an integrative approach, three new mayfly species of Epeorus (Caucasiron) are described. These include Epeorus (Caucasiron) alborzicus Hrivniak & Sroka, sp. nov. and Epeorus (Caucasiron) shargi Hrivniak & Sroka, sp. nov. from northern Iran, and Epeorus (Caucasiron) zagrosicus Hrivniak & Sroka, sp. nov. from central Iran. They are unambiguously delimited using both distance-based and likelihood-based approaches in the analyses of barcode COI sequences. Each new species is compared with other species of the subgenus and morphological diagnostic characters are provided. Based on extensive sampling of streams throughout the country, the distribution and habitat preferences of all Caucasiron species in Iran are assessed. Altogether, there are now six species recorded, among them also E. (C.) nigripilosus Sinitshenkova, 1976 is reported for the first time in Iran. Five species are distributed in the Alborz Mts. in northern Iran, one species was found in the Zagros Mts. in central Iran.

Studies on testate amoeba species distribution at small scales (i.e., single peatland sites) are rare and mostly focus on bogs or mineral-poor Sphagnum fens, leaving spatial patterns within mineral-rich fens completely unexplored. In this study, two mineral-rich fen sites of contrasting groundwater chemistry and moss layer composition were selected for the analysis of testate amoeba compositional variance within a single site. At each study site, samples from 20 randomly chosen moss-dominated plots were collected with several environmental variables being measured at each sampling spot. We also distinguished between empty shells and living individuals to evaluate the effect of empty shell inclusion on recorded species distribution. At the heterogeneous-rich Sphagnum-fen, a clear composition turnover in testate amoebae between Sphagnum-dominated and brown moss-dominated samples was closely related to water pH, temperature and redox potential. We also found notable species composition variance within the homogeneous calcareous fen, yet it was not as high as for the former site and the likely drivers of community assembly remained unidentified. The exclusion of empty shells provided more accurate data on species distribution as well as their relationship with some environmental variables, particularly moisture. Small-scale variability in species composition of communities seems to be a worthwhile aspect in testate amoeba research and should be considered in future sampling strategies along with a possible empty shell bias for more precise understanding of testate amoeba ecology and paleoecology.

Climate warming and associated environmental changes lead to compositional shifts and local extinctions in various ecosystems. Species closely associated with rare island-like habitats such as groundwater-dependent spring fens can be severely threatened by these changes due to a limited possibility to disperse. It is, however, largely unknown to what extent mesoclimate affects species composition in spring fens, where microclimate is buffered by groundwater supply. We assembled an original landscape-scale dataset on species composition of the most waterlogged parts of isolated temperate spring fens in the Western Carpathian Mountains along with continuously measured water temperature and hydrological, hydrochemical, and climatic conditions. We explored a set of hypotheses about the effects of mesoclimate air and local spring-water temperature on compositional variation of aquatic (macroinvertebrates), semi-terrestrial (plants) and terrestrial (land snails) components of spring-fen biota, categorized as habitat specialists and other species (i.e. matrix-derived). Water temperature did not show a high level of correlation with mesoclimate. For all components, fractions of compositional variation constrained to temperature were statistically significant and higher for habitat specialists than for other species. The importance of air temperature at the expense of water temperature and its fluctuation clearly increased with terrestriality, i.e. from aquatic macroinvertebrates via vegetation (bryophytes and vascular plants) to land snails, with January air temperature being the most important factor for land snails and plant specialists. Some calcareous-fen specialists with a clear distribution centre in temperate Europe showed a strong affinity to climatically cold sites in our study area and may hence be considered as threatened by climate warming. We conclude that prediction models solely based on air temperature may provide biased estimates of future changes in spring fen communities, because their aquatic and semiterrestrial components are largely affected by water temperature that is modified by local hydrological and landscape settings.

An initial checklist of mayflies (Ephemeroptera) of Iran is compiled based on critical review of available literature data, complemented with new data from 38 localities of Gilan and Ardabil provinces. At present, altogether only 46 species and 25 genera are known from Iran, 18 species are reported as new to Iran in this study. Some previously published data are critically evaluated and doubtful taxa are excluded from the list. Basic analysis of the distribution and biogeography of recorded species is given. Procloeon (Pseudocentroptilum) caspicum Sroka,sp. n.is described based on mature larva and egg. Critical differential diagnostic characters distinguishing the species from related taxa are discussed in detail.

Environmental factors driving compositional changes of headwater aquatic assemblages have been widely studied as these habitats are among the most vulnerable environments and host diverse and species-rich assemblages. However, responses of individual species to multiple environmental gradients remain poorly known, despite such information being essential for understanding the differences in metacommunity structuring. This study aims to explore species-specific responses to the main environmental gradients in Central European spring fens and to assess the responses in relation to the specialist-generalist categorization of species. In total, the responses of 40 species were analysed by GLM, cluster analysis and PCA. Spring-fen specialists responded predominantly to water temperature and the proportion of fine particulate organic matter in the substratum, while generalists responded mainly to flow conditions and oxygenation in the combination with various substratum characteristics. Our results revealed that it is not easy to find general patterns in species responses to environmental gradients. However, we found a clear distinction between specialist and generalist species in how the local environment affects their successful colonization and establishment of viable population. This result emphasizes the need to consider species specialization in future ecological studies of aquatic spring biota.

Two new species of the mayfly family Oligoneuriidae are described based on larval specimens recently collected in Iran. The first new species, Oligoneuriella tuberculata Godunko & Staniczek, sp. nov., can be distinguished from all its congeners by the presence of pronounced protuberances posteromedially on abdominal terga, highly reduced paracercus, large lamella of gill I, and setation on hind margin of middle and hind femora confined to their basal halves. The second species, Oligoneuriopsis villosus Bojková, Godunko, & Staniczek, sp. nov., remarkably belongs to a mostly Afrotropical genus. The new species clearly differs from all its congeners in the shape of setae on the surface of gills and terga, pattern of body colouration, and the shape of posterolateral projections of abdominal segments. Except for the species description, the generic diagnosis of Oligoneuriopsis Crass, 1947 is briefly discussed. COI barcode sequences of both new species are provided and molecular species delimitation is tested using distance-based and likelihood-based approaches, with both new species unambiguously recognised as separate lineages. The analysis of COI also corroborates the respective affinities of both new species, estimated based on morphology. The two new species of Oligoneuriidae described herein highlight the importance of the Middle East as a centre of diversity of this mayfly family within the Palaearctic.

Larval growth and maturation in aquatic insects are phenotypically plastic and can change in response to the amount and quality of resources, or under predation risk. While better food conditions typically lead to faster growth and earlier maturation at larger body size and hence higher fecundity, the effects of predation risk can vary depending on its strength and selectivity with respect to size or stage. Studies on lotic mayflies (Ephemeroptera) have reported two direct and two indirect life history responses to increased predation risk: slower growth rate and later maturation at the same or smaller size, and faster or unaltered growth rate and earlier maturation at smaller body size. However, life history responses of standing water mayflies to predation risk are unknown. To fill this gap, we carried out a full-factorial laboratory experiment to study the influence of food availability (full/reduced) and predation risk (present/absent predator cues) by dragonfly larvae on growth and maturation of larvae of the lentic mayfly Cloeon dipterum. Males and females responded similarly to food limitation and predation risk. Predation risk had no effect on maturation size, larval mortality and metamorphic failure. However, growth rate, number of moults and development time were all affected by predation risk, and its net effect was modified by food availability and initial body size of the larvae. These results suggest that life history responses to suboptimal conditions depend on body size at the onset of such conditions. Finally, a small group of larvae grew at much slower rates and developed much longer than other individuals of similar initial size, possibly due to bet-hedging or inclusion of multiple genotypes in the experiment.

Habitat specialists and generalists are known to differ in their width of environmental tolerance and their representation can vary along with the ecological contrast of habitats. In this study we explore factors shaping patterns of species richness and abundance of aquatic macroinvertebrate habitat specialists and generalists at isolated spring fens, separately for spring patch and spring brook mesohabitats at each site. We also examined habitat contrast of these unique island-like communities by the comparison of spring fen specialists and habitat generalists shared between the two spring fen mesohabitats and the nearest stream to each of 13 selects fen sites. Aquatic macroinvertebrates (Clitellata, Ephemeroptera, Plecoptera, Trichoptera, and Diptera) were investigated at 62 isolated spring fens, with 357 taxa identified in more than 172,000 individuals collected. We found that specialists experienced a stronger relation to local environmental conditions (i.e. the amount of dissolved oxygen and water conductivity) at both spring mesohabitats than generalists, primarily responding to fen habitat size. In contrast, responses of species abundances at spring patches and spring brooks differed as the abundances were controlled by the amount of oxygen in spring patches and by habitat size in spring brooks. Based on Trichoptera and Diptera assemblages we found a similar contrast between both spring fen sites and nearby streams. Our results suggest a higher resilience of specialist populations in well oxygenated sites and their competitive advantage over generalists at these sites, which stresses the importance to prevent any significant decrease of oxygenation (e.g., by eutrophication or drainage), especially in spring patches.

The response of planktonic (phytoplankton, ciliates, rotifers and crustaceans) and littoral (Ephemeroptera, Plecoptera, Trichoptera and Heteroptera: Nepomorpha) assemblages to chemical recovery was studied over a twelve-year period (1999–2011) in eight glacial lakes in the Bohemian Forest (central Europe). The region suffered from high atmospheric pollution from the 1950s to the late 1980s, but has since been recovering from acidification due to 86% and 44% decrease in sulphur and nitrogen deposition, respectively, during the 1990s–2000s. Despite the rapid improvement in water chemistry of all the eight studied lakes, only four have partly recovered so far (low-aluminium lakes), while the other four lakes still remain strongly acidic (high-aluminium lakes). Although biotic responses (especially in the low-Al lakes) showed important signs of recovery, such as reappearance of some indigenous or acid-sensitive species, decline in eurytopic acid-tolerant species and colonisation by vagile species, the assemblages of all the lakes still suffer from acid stress. Our results also indicate an increasing role of biotic interactions between colonisers and residents leading to the reconstruction of aquatic food webs in the low-Al lakes.

A common hypothesis for the high biodiversity of mountains is the diversification driven by orogeny creating conditions for rapid in situ speciation of resident lineages. The Caucasus is a young mountain system considered as a biodiversity hotspot; however, the origin and evolution of its diversity remain poorly understood. This study focuses on mayflies of the subgenus Caucasiron, one of the most diversified stenotopic mayflies inhabiting various types of streams throughout the Caucasus. Using the time-calibrated phylogeny based on two mitochondrial (COI, 16S) and three nuclear (EF-1α, wg, 28S) gene fragments, we tested the role of Caucasian orogeny in biogeography, diversification patterns, and altitudinal diversification of Caucasiron mayflies. We found that orogeny promoted the lineage diversification of Caucasiron in the Miocene. The highest diversification rate corresponding with the uplift of mountains was followed by a significant slowdown towards the present suggesting minor influence of Pleistocene climatic oscillations on the speciation. The Caucasiron lineages cluster into three principal clades originating in the Upper Miocene. We found a strong support that one of the three clades diversified via allopatric speciation in the Greater Caucasus isolated in the Parathetys Sea. The other two clades originating most likely outside the Greater Caucasus diversified towards high and low altitude, respectively, indicating possible role of climatic factors and/or passive uplift on their differentiation. Current high Caucasiron diversity in the Greater Caucasus is a result of in situ speciation and later immigration from adjacent mountain ranges after the Parathetys Sea retreat. Our phylogeny supported the monophyly of Rhithrogeninae, Epeorus s.l., Caucasiron, and Iron. Epeorus subgenus Ironopsis was found paraphyletic, with its European representatives more closely related to Epeorus s.str. than to Iron. Therefore, we re-arranged taxa treated within Ironopsis to comply with the phylogeny recovered herein.

Aims The aim was to identify the main drivers of aquatic macroinvertebrate species richness in spring-fen habitats (i.e. groundwater seepage wetlands) because these habitats are among the most threatened temperate biodiversity hotspots. Location Isolated spring fens in the western Carpathian Mountains. Methods Assemblages of Tricladida, Clitellata, Mollusca, Ephemeroptera, Plecoptera, Trichoptera and Diptera were sampled at 48 fens distributed evenly along a gradient of water mineral richness and grouped according to habitat specialization and dispersal mode. Several physicochemical parameters that have been reported to be the main drivers of species distribution were recorded for each site, along with radiocarbon measurements of the absolute age of the sites. The numbers of species in the taxonomic groups analysed were modelled as a function of the predictors via multiple linear regressions. Results We achieved a notably higher sampling efficiency than had been used in previous spring aquatic macroinvertebrate studies. In total, we collected and identified 255 species within 331 taxa from > 235,000 individuals. The number of species in all taxonomic groups increased with water discharge but the highest predictive power was obtained with water redox potential, which explained as much as 55.7% of the specialist species richness variance. We found contrasting and systematic differences in the importance of predictors related mainly to the level of species habitat specialization. Species richness of springfen specialists was strongly determined by the main environmental gradient of change in groundwater chemistry, while generalists primarily reflected habitat stability linked to higher water discharge, habitat size and absolute age. Main conclusion Isolated island-like spring fens can harbour unusually species-rich assemblages of aquatic macroinvertebrates, the species richness of which is shaped by contrasting mechanisms dependent mainly on habitat specialization and also partly on dispersal mode. The richness of habitat specialist species seen at calcareous fens indicates their conservation priority.

The effect of environment and species dispersal limitations may both significantly affect the structure of ecological metacommunities but there have been a relatively few attempts to separate their effects in aquatic assemblages. In this paper, we tested the relative importance of environment and space on the ostracod assemblages on a regional scale (encompassing ca 15,800 km2) in 74 permanent helocrene springs. We used Canonical Correspondence Analysis and Variation Partitioning to test the unique and shared effects of environment and space, represented by Principal Coordinates of Neighbor Matrices. We found that ostracod assemblages were significantly influenced by environment (mainly the mineral content and TOC) and space (roughly the west-east direction); the shared effect was relatively low. A unique effect of space was found for both species strongly associated with spring habitats and for euryoecious species found in the springs. We suggest that the passive dispersal in ostracods is random and infrequent between the isolated spring fens and produces spatially structured assemblages.

1. Large-scale and intensive human activities have caused widespread and profound changes in the diversity and structure of biological communities. Historical or long-term data are an important tool for the quantification and understanding of temporal changes. A comparison of Ephemeroptera collected at 60 streams in the Morava and Odra river basins in two periods, 1955–1960 and 2006–2011, enabled an estimate of changes in their assemblages induced by various human pressures to be made. 2. The taxonomic composition of mayfly assemblages was substantially dissimilar between the two periods, although the changes were not associated with a decline in regional or local diversity. Only lowland rivers lost several of their original species, mostly habitat specialists. Species replacement, a leading driver of dissimilarity, caused shifts towards more simplified, less specialized assemblages in large rivers, and towards more pollutionand siltation-tolerant assemblages in small rivers. The increase in cold-water specialists and a stable share of generalists suggested the maintenance of a certain level of specialization in the assemblages of brooks. 3. The most marked change in the assemblage was associated with the impaired or bad water quality of rivers in the 1950s, which persisted or further deteriorated in the ensuing decades. Assemblages that were influenced by a slight deterioration or improvement in water quality were less altered, unless affected by other pressures (such as channel or discharge modifications). 4. The results indicate that the causes of changes in the assemblages are many and complex, although heavy pollution overrides other influences. Direct habitat loss or their degradation by siltation appear to be leading contributors to changes in assemblages. The results imply the need for the application of a catchment-scale perspective for the restoration of streams and the conservation of the remaining well-preserved stretches of lowland rivers.

The relevance of environmental and spatial processes for species distributions varies among environments and types of metacommunities. Here, for the first time, we use modern statistical approaches to test the contribution of these two processes in structuring ecologically unique and threatened biotas of insular spring fens. We applied two species categorisations, common/rare and generalists/specialists, to disentangle the roles of dispersal capacity and habitat specialisation. In accordance with current understanding of headwater ecosystems, we found that environmental processes played a major role in most of the spring fen taxonomic and functional groups. However, we observed significant spatial structure in passive dispersers (Clitellata, a class of annelid worms), common species and habitat specialists. Spatial processes played the leading role in structuring the metacommunity of passively dispersing specialists. In contrast, all analysed insect groups, even those known to be poor dispersers, were able to reach virtually all favourable sites. We conclude that dispersal mode (active versus passive) and, to a lesser extent, habitat specialisation are the main factors determining the mechanism of spring fen metacommunity structuring.

This study provides new information on beta diversity (variation in species composition across space) of three invertebrate groups (Clitellata, Plecoptera, and Chironomidae) on a small, within-site spatial scale. It was conducted at small-sized spring fens where two contrasting mesohabitats, a flowing-water and a standing-water, can be clearly distinguished. Besides flow conditions, these habitats differed in the amounts of inorganic substratum and dissolved oxygen. Factors related to flow conditions (dissolved oxygen and water temperature) influenced the composition of the studied assemblages at both mesohabitats, while substratum features were important at the standing-water habitat. The water chemistry was important for Clitellata at both mesohabitats and for Chironomidae at the flowing-water. Using a new approach of disentangling beta diversity into two components (species replacement and species richness differences), clear difference in beta diversity patterns among the three assemblages were found, despite their roughly equal total beta diversities. Variation in species composition of those assemblages strongly limited by flow conditions (Plecoptera and partly Clitellata) was induced by differences in species richness, while replacement governed the variation in species rich assemblages that were able to utilise a wide range of conditions (Chironomidae and partly Clitellata). These results indicate that the size of species pool and the level of environmental filtering play an important role in forming beta diversity patterns, and caution that the same amount of beta diversity can be promoted by essentially different mechanisms, even at a very fine spatial scale with no involvement of dispersal limitations. (C) 2014 Elsevier GmbH. All rights reserved.

An unusual data set of Plecoptera, very sensitive aquatic insects, allow diversity changes to be estimated for 175 streams in the Czech Republic between two periods, 1955–1960 and 2006–2011. Substantial overall declines in Plecoptera biodiversity were found. Three quarters of the species studied declined in their frequency of occurrence, 48% of which were estimated have undergone a reduction of >30%. Overall, streams either at lowland or submontane altitude, particularly large rivers, lost the most species. A significant decrease in local species biodiversity was found in streams up to 700 m a.s.l., especially in small rivers. The taxonomic dissimilarity between contemporary and previous assemblages increased from montane to lowland altitudes (from ~30 to ~70%) and was the same in streams of different size (~50%). Partitioning of dissimilarity showed that the overall change in dissimilarity was primarily driven by changes in species richness; however, species replacement was not negligible. The results demonstrated that aquatic insect biodiversity (Plecoptera in particular) is substantially declining in Europe, probably to a similar or greater extent than terrestrial insects, with potential implications for biodiversity of running waters. Plecoptera showed a complex response to habitat change, including loss of pollution-sensitive species and habitat-specialists as well as common species, which, in some cases, counterbalanced their losses by concurrent colonisation of new sites.

Groundwater chemistry is a major determinant of assemblages of various taxonomic groups in spring fens, but its effect on insect assemblages has not been proved yet. We investigated dipteran assemblages at 17 isolated spring fens, which encompass the whole mineral richness gradient from rich (calcareous) to poor (highly acidic) sites, and analyzed faunal patterns at two contrasting mesohabitats: flowing water and standing water. The effect of water chemistry, substratum features, dis- charge, and temperature on the dipteran assemblages were assessed using PERMANOVA and GAM. Highly diverse dipteran assemblages (156 taxa) were closely related to the mineral richness gradient at both mesohabitats, showing a continual and nearly complete species exchange along the gradient, while their total abundance and taxa density did not change significantly. The assemblages included both habitat generalists and taxa specifically associated with acidic, moderate, or calcareous condi- tions. The mineral richness gradient was also reflected by changes in substratum properties, thus creating a complex environ- mental gradient that we suggest is the main environmental gradient structuring aquatic assemblages in spring fens. Resume : Si la chimie de l'eau souterraine est un des principaux determinants des assemblages de differents groupes taxi- nomiques dans les tourbieres minerotrophes de source, son incidence sur les assemblages d'insectes n'a pas encore ete demon- tree. Nous avons etudie les assemblages de dipteres dans 17 tourbieres minerotrophes de source isolees representatifs de tout le gradient de richesse minerale, allant de sites riches (calcaire) ades sites pauvres (tres acide), et analyse les distributions d'especes dans deux mesohabitats distincts, celui d'eau mouvante et celui d'eau stagnante. Les effets de la chimie de l'eau, des caracteri- stiques du substrat, du debit et de la temperature sur les assemblages de dipteres ont ete evalues al'aide des logiciels PERMANOVA et GAM. Des assemblages de dipteres tres varies (156 taxons) etaient etroitement relies au gradient de richesse minerale dans les deux mesohabitats, indiquant un echange d'especes continu et presque complet le long du gradient, sans changement significatif de leur abondance totale et de la densite de taxons. Les assemblages comprenaient tant des especes generalistes sur le plan de l'habitat que des taxons specifiquement associes ades conditions acides, moderees ou calcaires. Le gradient de richesse minerale se refletait egalement dans les variations des proprietes du substrat, creant ainsi un gradient environnemental complexe, que nous interpretons comme constituant le principal gradient environnemental structurant les assemblages aquatiques dans les tourbieres minerotrophes de source. (Traduit par la Redaction)

We examined the associations of microorganism assemblages with a complete mineral richness gradient spanning from extremely mineral-rich tufa-forming calcareous fens to mineral-poor acidic Sphagnum -fens. We also compared the distribution of two dominant taxa, testate amoebae and monogonont rotifers, among the sites differing in water chemistry and among three microhabitats sampled at each site differing in substrate and moisture conditions. Microorganism assemblages primarily changed in relation to the mineral richness gradient; moisture was the second most important factor structuring microorganism assemblages among microhabitats (i.e. , wet bryophytes, submerged bryophytes and waterlogged bottom sediments). Densities of testate amoebae taxa and individuals were the highest in rich Sphagnum -fens, indicating a unimodal pattern along the mineral richness gradient. Numbers of testate amoebae taxa decreased notably in wet bryophytes, especially in poor Sphagnum -fens. This pattern might result from a strong effect of Sphagnum acidification due to minimal or no dilution of the acidic environment by mineral-rich groundwater. As a consequence, acid tolerant and relatively xerophilous taxa chiefly dominated in wet bryophytes of poor Sphagnum -fens, while poor Sphagnum -fen bottom sediments could provide a refuge for less tolerant and hydrophilous species. In contrast to testate amoebae, monogonont rotifers preferred bryophytes in all sites, with the number of monogonont taxa distinctly increasing from calcareous fens to poor Sphagnum -fens. In poor Sphagnum -fens, monogononts were the most abundant in wet bryophytes, probably due to reduced food competition and/or predaceous pressure resulting from the limited occurrence of other groups of microorganisms by virtue of the hostile acidic conditions in wet Sphagnum carpets.

1. Rapid expansion and intensification of anthropogenic activities in the 20th century has caused profound changes in freshwater assemblages. Unfortunately, knowledge of the extent and causes of species loss (SL) is limited due to the lack of reliable historical data. An unusual data set allows us to compare changes in the most sensitive of aquatic insect orders, the Plecoptera, at some 170 locations in the Czech Republic between two time periods, 19551960 and 20062010. Historical data (18901911) on assemblages of six lowland rivers allow us to infer even earlier changes. 2. Regional stonefly diversity decreased in the first half of the 20th century. Streams at lower altitudes lost a substantial number of species, which were never recovered. In the second half of the century, large-scale anthropogenic pressure caused SL in all habitats, leading to a dissimilarity of contemporary and previous assemblages. The greatest changes were found at sites affected by organic pollution and a mixture of organic pollution and channelisation or impoundment. Colonisation of new habitats was observed in only three of the 80 species evaluated. 3. Species of moderate habitat specialisation and tolerance to organic pollution were most likely to be lost. Those with narrow specialisations in protected habitats were present in both historical and contemporary collections. 4. Contemporary assemblages are the consequence of more than a 100 years of anthropogenic impacts. In particular, streams at lower altitude and draining intensively exploited landscapes host a mere fragment of the original species complement. Most stonefly species are less frequently present than before, although their assemblages remain almost intact in near-natural mountain streams. Our analyses demonstrate dramatic restriction of species ranges and, in some cases, apparent changes in altitudinal preference throughout the area.

We examined responses of macroinvertebrate assemblages to environmental and temporal variations along spring source-spring brook transects in two fen habitats, sharply differing in groundwater chemistry, and compared the patterns among individual taxonomical groups. We hypothesised a different importance of environmental heterogeneity and seasonal changes primarily linked to strong tufa precipitation, which causes stronger environmental filtering in the calcareous fen. In concordance, we observed that assemblages of the more homogenous calcareous fen primarily changed over time, due to seasonal shifts in source availability and favourable conditions.

Spring fens are isolated treeless wetlands of a high conservation value. Their environmental conditions are strongly related to their groundwater chemistry, which controls species distribution within various groups of organisms. Clitellates, a dominant group of non-insect aquatic fauna, however, have never been studied in these habitats. It is unclear from previous studies to what extent the distribution of aquatic non-insect taxa reflects water chemistry rather than the substrate structure. We studied 34 spring fens sampled in 17 isolated sites in the Western Carpathian Mountains to determine mainly the effects of water chemistry and substrate structure on variation in species richness and composition of clitellate assemblages as examples of the non-insect fauna. A total of 34 taxa were found, with 3–15 taxa collected per sample. Species richness was negatively correlated with water mineral concentration measured as water electric conductivity (r = −0.57, P < 0.001) and positively with TOC (r = 0.60, P < 0.001). Surprisingly, the lowest number of taxa was found in calcareous fens and richness increased towards Sphagnum-fens. There was a species turnover related to changes in mineral richness and substrate characters. The main change of species composition was promoted by changes in substrate structure. The second gradient of species composition was linked with the amount of nutrients, moisture, and dominance of sphagna, and was associated with an increase of eurytopic species in fens with high nutrient availability. It was difficult to separate the effects of water chemistry and substrate on clitellate species distributions owing to the fact that variation in tufa precipitation and vegetation was driven by water chemistry changes. This study presented the first quantitative data on fen clitellate assemblages, which appear to have an unusual pattern of species richness. In contrast to plants and molluscs, calcareous fens appeared to be a harsh environment for clitellate species. Only few specialized species, mainly Trichodrilus strandi, were able to establish viable populations. The significant effect of water chemistry on clitellate distribution patterns raises questions about the direct influence of water chemistry on non-insect aquatic taxa, which have previously been considered to be mostly determined by substrate characteristics.