Contrasting patterns and mechanisms of spatial turnover for native and exotic freshwater fish in Europe

Aim We compare the distribution patterns of native and exotic freshwater fish in Europe, and test whether the same mechanisms (environmental filtering and/or dispersal limitation) govern patterns of decrease in similarity of native and exotic species composition over geographical distance (spatial species turnover). Locations Major river basins of Europe. Methods Data related to geography, habitat diversity, regional climate and species composition of native and exotic freshwater fish were collated for 26 major European river basins. We explored the degree of nestedness in native and exotic species composition, and quantified compositional similarity between river basins according to the beta‐sim (independent of richness gradient) and Jaccard (dependent of richness gradient) indices of similarity. Multiple regression on distance matrices and variation‐partitioning approaches were used to quantify the relative roles of environmental filtering and dispersal limitation in shaping patterns of decreasing compositional similarity over geographical distance. Results Native and exotic species exhibited significant nested patterns of species composition, indicating that differences in fish species composition between river basins are primarily the result of species loss, rather than species replacement. Both native and exotic compositional similarity decreased significantly with increasing geographical distance between river basins. However, gradual changes in species composition with geographical distance were found only for exotic species. In addition, exotic species displayed a higher rate of similarity decay (higher species turnover rate) with geographical distance, compared with native species. Lastly, the majority of explained variation in exotic compositional similarity was uniquely related to geography, whereas native compositional similarity was either uniquely explained by geography or jointly explained by environment and geography. Main conclusions Our study suggests that large‐scale patterns of spatial turnover for exotic freshwater fish in Europe are generated by human‐mediated dispersal limitation, whereas patterns of spatial turnover for native fish result from both dispersal limitation relative to historical events (isolation by mountain ranges, glacial history) and environmental filtering.     

Distance decay of similarity in freshwater communities: do macro‐ and microorganisms follow the same rules?

Aim An intensively debated issue in macroecology is whether unicellular organisms show biogeographic patterns different from those of macroorganisms. One aspect of this debate addresses beta diversity, that is, do microbial organisms exhibit distance‐decay patterns similar to those of macroorganisms? And if so, is the decay of community similarity caused by spatially limited dispersal or by niche‐related factors? We studied the community similarity of stream diatoms, macroinvertebrates and bryophytes across the same set of sites in relation to environmental and geographic distance. Location A geographical gradient of c. 1100 km in Finland. Methods We first identified the subset of environmental variables that produced the highest correlation with community similarities for each taxonomic group. Based on these variables, we used partial Mantel tests to separate the independent influences of environmental and geographical distance for distance decay of community similarity, separately for diatoms, bryophytes and macroinvertebrates. Finally, macroinvertebrates were divided into three groups based on their different dispersal categories and a partial Mantel test was used to assess whether each of these groups were differently affected by environmental versus geographic distance, i.e. is dispersal a key factor in tests of niche versus neutral models. Results The level of environmental control was by far the strongest for diatoms; however, all groups were controlled more by environmental factors than by limited dispersal. Macroinvertebrate species with low dispersal ability were significantly related to geographic distance, while more effective dispersers showed no relationship to geography but were instead strongly related to environmental distance. Main conclusions Our results suggest that patterns between macro‐ and microorganisms are not fundamentally different, but the level of environmental control varies according to dispersal ability. The relative importance of niche versus dispersal processes is not simply a function of organism size but other traits (e.g. life‐history type, dispersal capacity) may obscure this relationship.     

Gauging scale effects and biogeographical signals in similarity distance decay analyses: an Early Jurassic ammonite case study

In biogeography, the similarity distance decay (SDD) relationship refers to the decrease in compositional similarity between communities with geographical distance. Although representing one of the most widely used relationships in biogeography, a review of the literature reveals that: (1) SDD is influenced by both spatial extent and sample size; (2) the potential effect of the phylogenetic level has yet to be tested; (3) the effect of a marked biogeographical structuring upon SDD patterns is largely unknown; and (4) the SDD relationship is usually explored with modern, mainly terrestrial organisms, whereas fossil taxa are seldom used in that perspective. Using this relationship, we explore the long‐distance dispersal of the Early Jurassic (early Pliensbachian, c. 190.8 Ma to 187.6 Ma) ammonites of the western Tethys and adjacent areas, in a context of marked provincialism. We show that the long‐distance dispersal of these ammonites is not related to shell size and shape, but rather to the environmental characteristics of the province to which they belong. This suggests that their long‐distance dispersal may have been essentially driven by passive planktonic drift during early juvenile, post‐hatching stages. Furthermore, it seems that the SDD relationship is not always an appropriate method to characterize the existence of a biogeographical structuring. We conducted SDD analyses at various spatial, sampling and phylogenetic scales in order to evaluate their sensitivity to scale effects. This multi‐scale approach indicates that the sampling scale may influence SDD rates in an unpredictable way and that the phylogenetic level has a major impact on SDD patterns.     

Primate communities are structured more by dispersal limitation than by niches

1.?A major goal in community ecology is to identify mechanisms that govern the assembly and maintenance of ecological communities. Current models of metacommunity dynamics differ chiefly in the relative emphasis placed on dispersal limitation and niche differentiation as causal mechanisms structuring ecological communities. Herein we investigate the relative roles of these two mechanisms in structuring primate communities in Africa, South America, Madagascar and Borneo. 2.?We hypothesized that if dispersal limitation is important in structuring communities, then community similarity should depend on geographical proximity even after controlling for ecological similarity. Conversely, if communities are assembled primarily through niche processes, then community similarity should be determined by ecological similarity regardless of geographical proximity. 3.?We performed Mantel and partial Mantel tests to investigate correlations among primate community similarity, ecological distance and geographical distance. Results showed significant and strongly negative relationships between diurnal primate community similarity and both ecological similarity and geographical distance in Madagascar, but significant and stronger negative relationships between community similarity and geographical distance in African, South American and Bornean metacommunities. 4.?We conclude that dispersal limitation is an important determinant of primate community structure and may play a stronger role in shaping the structure of some terrestrial vertebrate communities than niche differentiation. These patterns are consistent with neutral theory. We recommend tests of functional equivalence to determine the extent to which neutral theory may explain primate community composition.     

The biogeography of parasitism in sticklebacks: distance,habitat differences and the similarity in parasite occurrence and abundance

Similarity in parasite community composition often decreases with both increasing geographic distance and environmental dissimilarity between localities, though it is unknown whether similarity in local abundance of selected parasite species follows similar rules. We tested this using data on metazoan parasites in 126 stickleback (Gasterosteus aculeatus) populations, with locations from Eurasia, eastern North America, and western North America treated separately. Similarity values were regressed against pairwise distances between localities; after correcting for distance, the effect of environmental dissimilarity was assessed by splitting similarity values into those between pairs of localities with either similar, moderately different or very different salinity (freshwater, marine or brackish). For selected parasite species, pairwise similarity in abundance (mean no. parasites per host) were computed across all localities, and treated as above. Similarity in parasite community composition decreased with increasing distance between localities in all three geographic regions. A significant effect of environmental difference was found in all regions: for a given distance between two sites, their parasite communities were more similar if they were of the same salinity. Slopes for distance decay in similarity were consistently higher for eastern North America than for Eurasia. Among the 12 parasite species for which sufficient data were available, only 4 showed the expected relationship, i.e. the greater the geographical separation between host populations, the greater the difference in parasite abundance; also, significant effects of environmental differences in salinity were only found for 3 of these species. Our findings show that parasite communities of sticklebacks are structured by geographical distance and local salinity conditions. The results indicate that strong effects at the community level do not translate into corresponding effects at the population level, suggesting that parasite dispersal and population dynamics are controlled by different processes.     

Dispersal Ability Determines the Role of Environmental,Spatial and Temporal Drivers of Metacommunity Structure

Recently, community ecologists are focusing on the relative importance of local environmental factors and proxies to dispersal limitation to explain spatial variation in community structure. Albeit less explored, temporal processes may also be important in explaining species composition variation in metacommunities occupying dynamic systems. We aimed to evaluate the relative role of environmental, spatial and temporal variables on the metacommunity structure of different organism groups in the Upper Paraná River floodplain (Brazil). We used data on macrophytes, fish, benthic macroinvertebrates, zooplankton, periphyton, and phytoplankton collected in up to 36 habitats during a total of eight sampling campaigns over two years. According to variation partitioning results, the importance of predictors varied among biological groups. Spatial predictors were particularly important for organisms with comparatively lower dispersal ability, such as aquatic macrophytes and fish. On the other hand, environmental predictors were particularly important for organisms with high dispersal ability, such as microalgae, indicating the importance of species sorting processes in shaping the community structure of these organisms. The importance of watercourse distances increased when spatial variables were the main predictors of metacommunity structure. The contribution of temporal predictors was low. Our results emphasize the strength of a trait-based analysis and of better defining spatial variables. More importantly, they supported the view that “all-or- nothing” interpretations on the mechanisms structuring metacommunities are rather the exception than the rule.     

Geographical distribution of zooplankton biodiversity in highly polluted running water ecosystems: Validation of fine‐scale species sorting hypothesis

Dispersal, rather than species sorting, is widely recognized as the dominant driver for determining meta‐community structure at fine geographical scales in running water ecosystems. However, this view has been challenged by a recently proposed “fine‐scale species sorting hypothesis,” where community structure can be largely determined by an environmental gradient formed by local pollution at fine scales. Here, we tested this hypothesis by studying community composition and geographical distribution of metazoan zooplankton in a heavily polluted river—the North Canal River in the Haihe River Basin, China. Analysis of similarity (ANOSIM) showed that the community composition of metazoan zooplankton differed significantly (p = .001) along the environmental gradient. Ammonium (NH₄‐N) was the leading factor responsible for changes in zooplankton community structure and geographical distribution, followed by total dissolved solid (TDS), Na, dissolved oxygen (DO) and temperature (T). Variation partitioning revealed a larger contribution of environmental variables (21.6%) than spatial variables (1.1%) to the total explained variation of zooplankton communities. Our results support that species sorting, rather than dispersal, played a key role in structuring communities. Threshold Indicator Taxa ANalysis (TITAN) also revealed significant change points at both taxon and community levels along the gradient of NH₄‐N, providing further support for the influence of environmental variables on zooplankton communities. Collectively, we validate the fine‐scale species sorting hypothesis when an environmental gradient exists in running water ecosystems at fine geographical scales. However, future studies on interactions between pollutants and zooplankton communities are still needed to better understand mechanisms responsible for the meta‐community dynamics.     

Biogeographical patterns of abundant and rare bacterial biospheres in paddy soils across East Asia

Soil bacterial communities play fundamental roles in ecosystem functioning and often display a skewed distribution of abundant and rare taxa. So far, relatively little is known about the biogeographical patterns and mechanisms structuring the assembly of abundant and rare biospheres of soil bacterial communities. Here, we studied the geographical distribution of different bacterial sub-communities by examining the relative influence of environmental selection and dispersal limitation on taxa distributions in paddy soils across East Asia. Our results indicated that the geographical patterns of four different bacterial sub-communities consistently displayed significant distance–decay relationships (DDRs). In addition, we found niche breadth and dispersal rates to significantly explain differences in community assembly of abundant and rare taxa, directly affecting the strength of DDRs. While conditionally rare and abundant taxa displayed the strongest DDR due to higher environmental filtering and dispersal limitation, moderate taxa sub-communities had the weakest DDR due to greater environmental tolerance and dispersal rate. Random forest models indicated that soil pH (9.13%–49.78%) and average annual air temperature (16.59%–46.49%) were the most important predictors of the variation in the bacterial community. This study advances our understanding of the intrinsic links between fundamental ecological processes and microbial biogeographical patterns in paddy soils.     

T4-like myovirus community shaped by dispersal and deterministic processes in the South China Sea

As the most abundant and genetically diverse biological entities, viruses significantly influence ecological, biogeographical and evolutionary processes in the ocean. However, the biogeography of marine viruses and the drivers shaping viral community are unclear. Here, the biogeographic patterns of T4-like viruses and the relative impacts of deterministic (environmental selection) and dispersal (spatial distance) processes were investigated in the northern South China Sea. The dominant viral operational taxonomic units were affiliated with previously defined Marine, Estuary, Lake and Paddy Groups. A clear viral biogeographic pattern was observed along the environmental gradient from the estuary to open sea. Marine Groups I and IV had a wide geographical distribution, whereas Marine Groups II, III and V were abundant in lower-salinity continental or eutrophic environments. A significant distance-decay pattern was noted for the T4-like viral community, especially for those infecting cyanobacteria. Both deterministic and dispersal processes influenced viral community assembly, although environmental selection (e.g. temperature, salinity, bacterial abundance and community, etc.) had a greater impact than spatial distance. Network analysis confirmed the strong association between viral and bacterial community composition, and suggested a diverse ecological relationship (e.g. lysis, co-infection or mutualistic) between and within viruses and their potential bacterial hosts.     

Biogeographical patterns of rocky intertidal communities along the Pacific coast of North America

Aim Our aim in this paper is to present the first broad‐scale quantification of species abundance for rocky intertidal communities along the Pacific coast of North America. Here we examine the community‐level marine biogeographical patterns in the context of formerly described biogeographical regions, and we evaluate the combined effects of geographical distance and environmental conditions on patterns of species similarity across this region. Location Pacific coast of North America. Methods Data on the percentage cover of benthic marine organisms were collected at 67 rocky intertidal sites from south‐eastern Alaska, USA, to central Baja California Sur, Mexico. Cluster analysis and non‐metric multidimensional scaling were used to evaluate the spatial patterns of species similarity among sites relative to those of previously defined biogeographical regions. Matrices of similarity in species composition among all sites were computed and analysed with respect to geographical distance and long‐term mean sea surface temperature (SST) as a measure of environmental conditions. Results We found a high degree of spatial structure in the similarity of intertidal communities along the coast. Cluster analysis identified 13 major community structure ‘groups’. Although breaks between clusters of sites generally occurred at major biogeographical boundaries, some of the larger biogeographical regions contained several clusters of sites that did not group according to spatial position or identifiable coastal features. Additionally, there were several outliers – sites that grouped alone or with sites outside their region – for which localized features may play an important role in driving community structure. Patterns of species similarity at the large scale were highly correlated with geographical distance among sites and with SST. Importantly, we found community similarity to be highly correlated with long‐term mean SST while controlling for the effects of geographical distance. Main conclusions These findings reveal a high degree of spatial structure in the similarity of rocky intertidal communities of the north‐east Pacific, and are generally consistent with those of previously described biogeographical regions, with some notable differences. Breaks in similarity among clusters are generally coincident with known biogeographical and oceanographic discontinuities. The strong correlations between species similarity and both geographical position and SST suggest that both geography and oceanographic conditions have a large influence on patterns of intertidal community structure along the Pacific coast of North America.     

Applying landscape genetics to the microbial world

Landscape genetics, which explicitly quantifies landscape effects on gene flow and adaptation, has largely focused on macroorganisms, with little attention given to microorganisms. This is despite overwhelming evidence that microorganisms exhibit spatial genetic structuring in relation to environmental variables. The increasing accessibility of genomic data has opened up the opportunity for landscape genetics to embrace the world of microorganisms, which may be thought of as ‘the invisible regulators’ of the macroecological world. Recent developments in bioinformatics and increased data accessibility have accelerated our ability to identify microbial taxa and characterize their genetic diversity. However, the influence of the landscape matrix and dynamic environmental factors on microorganism genetic dispersal and adaptation has been little explored. Also, because many microorganisms coinhabit or codisperse with macroorganisms, landscape genomic approaches may improve insights into how micro‐ and macroorganisms reciprocally interact to create spatial genetic structure. Conducting landscape genetic analyses on microorganisms requires that we accommodate shifts in spatial and temporal scales, presenting new conceptual and methodological challenges not yet explored in ‘macro’‐landscape genetics. We argue that there is much value to be gained for microbial ecologists from embracing landscape genetic approaches. We provide a case for integrating landscape genetic methods into microecological studies and discuss specific considerations associated with the novel challenges this brings. We anticipate that microorganism landscape genetic studies will provide new insights into both micro‐ and macroecological processes and expand our knowledge of species’ distributions, adaptive mechanisms and species’ interactions in changing environments.     

Trophic relationships in the pelagic zone of Mondsee,Austria

Data are presented on nutrient concentrations, phytoplankton biovolume development, zooplankton composition and population dynamics, and fish from a deep, stratifying, alpine lake (Mondsee, Austria) during a three-year period between 1982 and 1984. Development of the phytoplankton is closely related to structuring events of the physico-chemical environment. Dissolved silicate and phosphorus concentrations are critical for the summer situation. During summer algal abundance is largely affected by grazing of zooplankton, but no clear-water phase was observed at the end of the spring peak of phytoplankton.Temperature and food are factors responsible for the timing and growth of the zooplankton populations. Because of close overlap in the epilimnion, exploitative and mechanical interference competition and predation by invertebrate and vertebrate predators are the main structuring forces acting on the zooplankton community, and hence influence phytoplankton indirectly.     

Effect of landscape context on fish metacommunity structuring in stream networks

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The role of environmental and spatial processes in structuring native and non‐native fish communities across thousands of lakes

Quantifying the role of spatial patterns is an important goal in ecology to further understand patterns of community composition. We quantified the relative role of environmental conditions and regional spatial patterns that could be produced by environmental filtering and dispersal limitation on fish community composition for thousands of lakes. A database was assembled on fish community composition, lake morphology, water quality, climatic conditions, and hydrological connectivity for 9885 lakes in Ontario, Canada. We utilized a variation partitioning approach in conjunction with Moran's Eigenvector Maps (MEM) and Asymmetric Eigenvector Maps (AEM) to model spatial patterns that could be produced by human‐mediated and natural modes of dispersal. Across 9885 lakes and 100 fish species, environmental factors and spatial structure explained approximately 19% of the variation in fish community composition. Examining the proportional role of spatial structure and environmental conditions revealed that as much as 90% of the explained variation in native species assemblage composition is governed by environmental conditions. Conversely on average, 67% of the explained variation in non‐native assemblage composition can be related to human‐mediated dispersal. This study highlights the importance of including spatial structure and environmental conditions when explaining patterns of community composition to better discriminate between the ecological processes that underlie biogeographical patterns of communities composed of native and non‐native fish species.     

Volcanic calderas delineate biogeographic provinces among Yellowstone thermophiles

It has been suggested that the distribution of microorganisms should be cosmopolitan because of their enormous capacity for dispersal. However, recent studies have revealed that geographically isolated microbial populations do exist. Geographic distance as a barrier to dispersal is most often invoked to explain these distributions. Here we show that unique and diverse sequences of the bacterial genus Sulfurihydrogenibium exist in Yellowstone thermal springs, indicating that these sites are geographically isolated. Although there was no correlation with geographic distance or the associated geochemistry of the springs, there was a strong historical signal. We found that the Yellowstone calderas, remnants of prehistoric volcanic eruptions, delineate biogeographical provinces for the Sulfurihydrogenibium within Yellowstone (χ²: 9.7, P  = 0.002). The pattern of distribution that we have detected suggests that major geological events in the past 2 million years explain more of the variation in sequence diversity in this system than do contemporary factors such as habitat or geographic distance. These findings highlight the importance of historical legacies in determining contemporary microbial distributions and suggest that the same factors that determine the biogeography of macroorganisms are also evident among bacteria.     

The effects of contemporary selection and dispersal limitation on the community assembly of acidophilic microalgae

Extremophilic microalgae are primary producers in acidic habitats, such as volcanic sites and acid mine drainages, and play a central role in biogeochemical cycles. Yet, basic knowledge about their species composition and community assembly is lacking. Here, we begin to fill this knowledge gap by performing the first large‐scale survey of microalgal diversity in acidic geothermal sites across the West Pacific Island Chain. We collected 72 environmental samples in 12 geothermal sites, measured temperature and pH, and performed rbcL amplicon‐based 454 pyrosequencing. Using these data, we estimated the diversity of microalgal species, and then examined the relative contribution of contemporary selection (i.e., local environmental variables) and dispersal limitation on the assembly of these communities. A species delimitation analysis uncovered seven major microalgae (four red, two green, and one diatom) and higher species diversity than previously appreciated. A distance‐based redundancy analysis with variation partitioning revealed that dispersal limitation has a greater influence on the community assembly of microalgae than contemporary selection. Consistent with this finding, community similarity among the sampled sites decayed more quickly over geographical distance than differences in environmental factors. Our work paves the way for future studies to understand the ecology and biogeography of microalgae in extreme habitats.     

Relative contributions of neutral and niche-based processes to the structure of a desert grassland grasshopper community

Whether neutral or deterministic factors structure biotic communities remains an open question in community ecology. We studied the spatial structure of a desert grassland grasshopper community and tested predictions for species sorting based on niche differentiation (deterministic) and dispersal limitation (neutral). We contrasted the change in species relative abundance and community similarity along an elevation gradient (i.e., environmental gradient) against community change across a relatively homogeneous distance gradient. We found a significant decrease in pairwise community similarity along both elevation and distance gradients, indicating that dispersal limitation plays a role in structuring local grasshopper communities. However, the distance decay of similarity was significantly stronger across the elevational gradient, indicating that niche-based processes are important as well. To further investigate mechanisms underlying niche differentiation, we experimentally quantified the dietary preferences of two common species, Psoloessa texana and Psoloessa delicatula, for the grasses Bouteloua eriopoda and Bouteloua gracilis, which are the dominant plants (~75% of total cover) in our study area. Cover of the preferred host plant explained some of the variation in relative abundances of the two focal species, although much variance in local Psoloessa distribution remained unexplained. Our results, the first to examine these hypotheses in arid ecosystems, indicate that the composition of local communities can be influenced by both probabilistic processes and mechanisms based in the natural histories of organisms.     

Zooplankton community structure along a pollution gradient at fine geographical scales in river ecosystems: The importance of species sorting over dispersal

The release of anthropogenic pollution into freshwater ecosystems has largely transformed biodiversity and its geographical distribution patterns globally. However, for many communities including ecologically crucial ones such as zooplankton, it is largely unknown how different communities respond to environmental pollution. Collectively, dispersal and species sorting are two competing processes in determining the structure and geographical distribution of zooplankton communities in running water ecosystems such as rivers. At fine geographical scales, dispersal is usually considered as the dominant factor; however, the relative role of species sorting has not been evaluated well, mainly because significant environmental gradients rarely exist along continuously flowing rivers. The Chaobai River in northern China represents a rare system, where a significant environmental gradient exists at fine scales. Here, we employed high‐throughput sequencing to characterize complex zooplankton communities collected from the Chaobai River, and tested the relative roles of dispersal and species sorting in determining zooplankton community structure along the pollution gradient. Our results showed distinct patterns of zooplankton communities along the environmental gradient, and chemical pollutant‐related factors such as total phosphorus and chlorophyll‐a were identified as the major drivers for the observed patterns. Further partial redundancy analyses showed that species sorting overrode the effect of dispersal to shape local zooplankton community structure. Thus, our results reject the dispersal hypothesis and support the concept that species sorting caused by local pollution can largely determine the zooplankton community structure when significant environmental gradients exist at fine geographical scales in highly polluted running water ecosystems.     

Hydrological connectivity structures concordant plant and animal assemblages according to niche rather than dispersal processes

1. Understanding the processes that structure community assembly across landscapes is fundamental to ecology and for predicting and managing the consequences of anthropogenically induced changes to ecosystems. 2. We assessed the community similarity of fish, macroinvertebrate and vegetation communities against geographic distances ranging from 4 to 480 km (i.e. distance–decay relationships) to determine the balance between local environmental factors and regional dispersal processes, and thus whether species‐sorting (niche processes) or dispersal limitation (neutral processes) was more important in structuring these assemblages in Australia’s wet‐dry tropics. We investigated whether the balance between niche and dispersal processes depended on the degree of hydrological connectivity, predicting that dispersal processes would be more important at connected sites, and also whether there was spatial concordance among these three assemblage types. 3. There was significant but weak spatial concordance among the study communities, suggesting limited potential for surrogacy among them. Distance–decay in community similarity was not observed for any study assemblage at perennial sites, suggesting dispersal was not limiting and assemblages were structured more strongly by local niche processes at these connected sites. At intermittent sites, weak distance–decay relationships for each assemblage type were confounded by significant relationships with environmental dissimilarity, suggesting that dispersal limitation contributed, albeit weakly, to niche processes in structuring our three study assemblages at disconnected sites. 4. Two environmental factors, flow regime and channel width, explained significant proportions of variation in all three assemblages, potentially contributing to the observed spatial concordance between them and representing local environmental gradients along which these communities re‐assemble after the wet season, according to niche rather than dispersal processes.     

Patterns of elevational beta diversity in micro‐ and macroorganisms

Aim While ecologists have long been interested in diversity in mountain regions, elevational patterns in beta diversity are still rarely studied across different life forms ranging from micro‐ to macroorganisms. Also, it is not known whether the patterns in turnover among organism groups are affected by the degree to which the environment is modified by human activities. Location Laojun Mountain, Yunnan Province, China. Methods The beta diversity patterns of benthic microorganisms (i.e. diatoms and bacteria) and macroorganisms (i.e. macroinvertebrates) in a stony stream were simultaneously investigated between elevations of 1820 and 4050 m. Data were analysed by using a distance‐based approach and variation partitioning based on canonical redundancy analysis. Results Analyses of community dissimilarities between adjacent sampling sites showed comparable small‐scale beta diversity along the elevational gradient for the organism groups. However, bacteria clearly showed the lowest elevational turnover when analyses were conducted simultaneously for all pairwise sites. Variation partitioning indicated that species turnover was mostly related to environmental heterogeneity and spatial gradients including horizontal distance and elevation, while purely human impacts were shown to be less important. Main conclusions The elevational beta diversity at large scales was lower for bacteria than for eukaryotic microorganisms or macroorganisms, perhaps indicative of high dispersal ability and good adaptability of bacteria to harsh environmental conditions. However, the small‐scale beta diversity did not differ among the groups. Elevation was the major driver for the turnover of eukaryotic organisms, while the turnover of bacteria was correlated more with environmental variation.