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Emilio A. Williams-Subiza Cecilia Brand M. Laura Miserendino 《Ecological Entomology》2020,45(6):1284-1295
- Understanding processes driving patterns of species distribution and diversity is one of the main objectives of community ecology.
- The aim of our study was to evaluate the spatial variation in assemblage composition of stream-dwelling macroinvertebrates and identify which factors (e.g. water quality, land cover) are the most important drivers.
- We applied the elements of the metacommunity structure approach on a dataset of 38 communities from the Futaleufú basin in northwestern Patagonia. To better understand assemblage variation, we deconstructed our macroinvertebrate dataset into different taxonomic and trait groups. We then identified the most influential factors driving community composition using random forests.
- We found that half of our datasets (i.e. macroinvertebrate groups) exhibited a nested structure with clumped species loss, while the other half showed a quasi-nested pattern with either clumped or stochastic species loss.
- Overall, water quality was the most important driver of community variation, although climate, geography, and land cover were more or less relevant in particular cases. We found differences in the relative importance of the selected explanatory variables among datasets. This would suggest that different components of the macroinvertebrate community respond differently to environmental factors.
- Our findings could be of value for conservation planning, as they suggest that preserving the most species-rich streams would, to some extent, guarantee the conservation of the entire species pool.
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- Metacommunities are structured by a combination of different ecological factors that vary in their importance depending on environmental heterogeneity and species functional equivalence. However, empirical tests of such context-dependence at regional scales are still missing.
- We investigated associations between deterministic (e.g. environmental filtering and biotic interactions) and stochastic factors (e.g. dispersal related) and metacommunity structure of macroinvertebrates and diatoms across streams in four regions with contrasting levels of environmental and organismal trait heterogeneity.
- Environmental filtering was most strongly associated with the region that showed moderate environmental heterogeneity and comprised communities with the highest trait heterogeneity. Associations with stochastic factors in the regions were more variable and difficult to predict. Environmental factors and the degree of genus-level association were generally more strongly associated with macroinvertebrates than with diatoms, whereas stochastic factors had consistently lower influence on macroinvertebrates.
- These results suggest that the degree to which deterministic versus stochastic factors influence aquatic metacommunities depends on environmental and trait heterogeneity. Furthermore, organismal characteristics such as dispersal potential, habitat specialisation and sensitivity to environmental variation can also generate considerable context dependency in metacommunity structure.
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Sophie Cauvy-Fraunié Rodrigo Espinosa Patricio Andino Dean Jacobsen Olivier Dangles 《PloS one》2015,10(8)
Under the ongoing climate change, understanding the mechanisms structuring the spatial distribution of aquatic species in glacial stream networks is of critical importance to predict the response of aquatic biodiversity in the face of glacier melting. In this study, we propose to use metacommunity theory as a conceptual framework to better understand how river network structure influences the spatial organization of aquatic communities in glacierized catchments. At 51 stream sites in an Andean glacierized catchment (Ecuador), we sampled benthic macroinvertebrates, measured physico-chemical and food resource conditions, and calculated geographical, altitudinal and glaciality distances among all sites. Using partial redundancy analysis, we partitioned community variation to evaluate the relative strength of environmental conditions (e.g., glaciality, food resource) vs. spatial processes (e.g., overland, watercourse, and downstream directional dispersal) in organizing the aquatic metacommunity. Results revealed that both environmental and spatial variables significantly explained community variation among sites. Among all environmental variables, the glacial influence component best explained community variation. Overland spatial variables based on geographical and altitudinal distances significantly affected community variation. Watercourse spatial variables based on glaciality distances had a unique significant effect on community variation. Within alpine catchment, glacial meltwater affects macroinvertebrate metacommunity structure in many ways. Indeed, the harsh environmental conditions characterizing glacial influence not only constitute the primary environmental filter but also, limit water-borne macroinvertebrate dispersal. Therefore, glacier runoff acts as an aquatic dispersal barrier, isolating species in headwater streams, and preventing non-adapted species to colonize throughout the entire stream network. Under a scenario of glacier runoff decrease, we expect a reduction in both environmental filtering and dispersal limitation, inducing a taxonomic homogenization of the aquatic fauna in glacierized catchments as well as the extinction of specialized species in headwater groundwater and glacier-fed streams, and consequently an irreversible reduction in regional diversity. 相似文献
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Salinisation reduces biodiversity in neighbouring freshwater patches in experimental metacommunities
- Aquatic ecosystems are biodiversity hot spots across many landscapes; therefore, the degradation of these habitats can lead to decreases in biodiversity across multiple scales. Salinisation is a global issue that threatens freshwater ecosystems by reducing water quality and local biodiversity. The effects of salinity on local processes have been studied extensively; however, the effects of salinisation or similar environmental stressors within a metacommunity (a dispersal network of several distinct communities) have not been explored.
- We tested how the spatial heterogeneity and the environmental contrast between freshwater and saline habitat patches influenced cladoceran biodiversity and species composition at local and regional scales in a metacommunity mesocosm experiment. We defined spatial heterogeneity as the proportion of freshwater to saltwater patches within the metacommunity, ranging from a freshwater-dominated metacommunity to a saltwater-dominated metacommunity. Environmental contrast was defined as the environmental distance between habitat patches along the salinity gradient in which low-contrast metacommunities consisted of freshwater and low-salinity patches and high-contrast metacommunities consisted of freshwater and high-salinity patches.
- We hypothesised that the α-richness of freshwater patches and metacommunity γ-richness would decrease as freshwater patches became less abundant along the spatial heterogeneity gradient in both low- and high-contrast metacommunities, because there would be fewer freshwater patches that could serve as source populations for declining populations. We hypothesised that low-contrast metacommunities would support more species across the spatial heterogeneity gradient than high-contrast metacommunities, because, via dispersal, low-salinity patches can support halotolerant freshwater species that can mitigate population declines in neighbouring freshwater patches, whereas` high-salinity patches will mostly support halophilic species, providing fewer potential colonisers to freshwater patches.
- We found that α-richness of freshwater mesocosms and metacommunity γ-richness declined in saline-dominated metacommunities regardless of the environmental contrast between the freshwater and saline mesocosms. We found that environmental contrast influenced freshwater and saline community composition in low-contrast metacommunities by increasing the abundances of species that could tolerate low-salinity environments through dispersal, whereas freshwater and high-salinity communities showed limited interactions through dispersal.
- Freshwater mesocosms had a disproportionate effect on the local and regional biodiversity in these experimental metacommunities, indicating that habitat identity may be more important than habitat diversity for maintaining biodiversity in some metacommunities. This study further emphasises the importance in maintaining multiple species-rich habitat patches across landscapes, particularly those experiencing landscape-wide habitat degradation.
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Understanding how species are distributed according to environmental and spatial variation is still one of the main issues in community ecology. We analysed the responses of semiaquatic bugs (Gerromorpha: Hemiptera) to environmental and spatial processes considered drivers of metacommunity structure in Amazonian streams. We tested the hypotheses that environmental variables determine the metacommunity structure and that the spatial structures, both dendritic and overland, are not representative of the metacommunity structure. Environmental variables and semiaquatic bugs were collected from 39 stream sites. Spatial variables were calculated in two configurations – overland and hydrographic distances between streams. We used partial redundancy analysis to test the relative importance of environment and space on the metacommunity structure, considering the two spatial configurations separately. The environmental variables were the metacommunity drivers in tropical streams, mainly structured by the depth, canopy, embeddedness and slope variables. Our results also indicate little or no dispersion limitation, as no spatial patterns were found. Thus, environmental selection determines the semiaquatic bugs' metacommunity structure due to the achievement of optimal habitats through dispersal. We also believe that dispersion cannot be ruled out as a metacommunity driver, since the peculiarities of the group show seasonal changes in dispersion ability, and spatial patterns may occur under different temporal scales. 相似文献
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David H. Keller 《Freshwater Biology》2023,68(1):12-24
- Determining the appropriate measurement scale to assess habitat variables is critical for ecologists assessing biological or ecological conditions. Depth, velocity, substrate, woody debris and other fish cover variables occur on both reach and microhabitat scales, and fish habitat associations with these variables may be scale-dependent. The aim of this work was to better understand the importance of scale for fish–habitat associations with these variables in a framework consistent with environmental filtering and to test the hypothesis that habitat variable importance is scale-dependent.
- I used prepositioned areal electrofishing in wadeable streams of the Delaware River basin to evaluate the associations of fish with the same variables summarised on different reach and microhabitat scales. The importance of scale for fish–habitat associations was assessed using two approaches that approximate an environmental filtering framework: variance partitioning with (1) ordination and (2) generalised linear mixed models.
- Variables on both the reach and microhabitat scales explained a significant fraction of the total variation in fish community composition (p < 0.05). Variation decomposition of reach- and microhabitat-scale effects revealed 20.2% and 2.0% of all variation were due uniquely to reach and microhabitat scales, respectively. Measures of coarseness, embeddedness, amount of riffle and areal coverage of five fish cover variables were significant explanatory variables of community composition at the reach scale only (p < 0.05). Velocity and mesohabitat (amount or presence of riffle) were the only two habitat features that were significant explanatory variables of fish community composition at both the reach and microhabitat scales (p < 0.05). Individual models of species occurrence revealed similar patterns as seen with analyses of community composition.
- For many fishes, habitat features quantified at the reach scale were more explanatory than at the microhabitat scale. Longnose dace (Rhinichthys cataractae) were more dependent upon microhabitat variables than reach-scale variables, relative to other fishes. Mean velocity at the reach scale was the most important explanatory variable for explaining fish community composition and indicated support for the concept of environmental filtering at the reach and microhabitat scales.
- Few studies of fish occurrence have incorporated a study design and analytical framework that approximates the hierarchical nature of habitat. This study identifies important scales and predictors, demonstrates the importance of a multiscale approach, and provides support for the environmental filtering concept at the reach and microhabitat scales. These findings will allow ecologists to better account for scale-dependent habitat associations and justify the use of fish habitat associations on reach and microhabitat scales for assessing biotic integrity, restoration and conservation of fishes.
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Relative influence of variables at multiple spatial scales on stream macroinvertebrates in the Northern Lakes and Forest ecoregion, U.S.A. 总被引：4，自引：0，他引：4
Brian M. Weigel Lizhu Wang Paul W. Rasmussen Jason T. Butcher Paul M. Stewart Thomas P. Simon Michael J. Wiley 《Freshwater Biology》2003,48(8):1440-1461
- 1 We used 94 sites within the Northern Lakes and Forests ecoregion spanning Minnesota, Wisconsin and Michigan to identify environmental variables at the catchment, reach and riparian scales that influence stream macroinvertebrates. Redundancy analyses (RDA) found significantly influential variables within each scale and compared their relative importance in structuring macroinvertebrate assemblages.
- 2 Environmental variables included landcover, geology and groundwater delivery estimates at the catchment scale, water chemistry, channel morphology and stream habitat at the reach scale, and landcover influences at three distances perpendicular to the stream at the riparian scale. Macroinvertebrate responses were characterised with 22 assemblage attributes, and the relative abundance and presence/absence of 66 taxa.
- 3 Each scale defined macroinvertebrates along an erosional to depositional gradient. Wisconsin's macroinvertebrate index of biotic integrity, Ephemeroptera–Plecoptera–Trichoptera taxa and erosional taxa corresponded with forest streams, whereas organic pollution tolerant, Chironomidae and depositional taxa corresponded with wetland streams. Reach scale analyses defined the gradient similarly as dissolved oxygen and wide, shallow channels (erosional) opposed instream macrophytes and pool habitats (depositional). Riparian forests within 30 m of the stream coincided with an erosional assemblage and biotic integrity.
- 4 Next, we combined all significant environmental variables across scales to compare the relative influence of each spatial scale on macroinvertebrates. Partial RDA procedures described how much of the explained variance was attributable to each spatial scale and each interrelated scale combination.
- 5 Our results appeared consistent with the concept of hierarchical functioning of scale in which large‐scale variables restrict the potential for macroinvertebrate traits or taxa at smaller spatial scales. Catchment and reach variables were equally influential in defining assemblage attributes, whereas the reach scale was more influential in determining relative abundance and presence/absence.
- 6 Ultimately, comprehending the relative influence of catchment and reach scale properties in structuring stream biota will assist prioritising the scale at which to rehabilitate, manage and derive policies for stream ecosystem integrity.