Metacommunity Framework Research Articles

Multiple‐stressor effects on leaf litter decomposition in freshwater ecosystems: A meta‐analysis

Abstract Recent years have witnessed a surge in research on the effects of multiple stressors in freshwater ecosystems. While studies have increased, the synthesis of their findings into a broader understanding of ecosystem‐level effects remains an ongoing endeavour. Leaf litter decomposition, a frequently investigated and pivotal ecosystem function in freshwaters, is sensitive to changes in abiotic conditions and biotic communities, and therefore susceptible to multiple‐stressor effects. Here, we synthesize findings from 27 manipulative experimental studies encompassing 61 responses of litter decomposition to paired stressors such as warming, nutrient enrichment and emerging pollutants in freshwater ecosystems. We calculated the individual and overall interaction effect sizes resulting from two stressors occurring simultaneously. Furthermore, we analysed the effect of moderator variables in the size and direction of interaction effect sizes using a meta‐analytical approach. Although the vote‐counting method showed additive interactions to dominate individual observations (91.8%), weighted random‐effects meta‐analysis revealed an overall antagonistic interaction between stressors (i.e. the cumulative effect of paired stressors on litter decomposition was less than the sum of their single effects). Our results emphasized the influence of experimental characteristics such as macroinvertebrate involvement, habitat type (lentic vs. lotic) and litter quality (assumed from plant mycorrhizal association) in shaping the responses of litter decomposition to multiple stressors. Our meta‐analysis highlights the need to incorporate local ecological complexities in manipulative experiments to improve predictions of multiple‐stressor effects on biodiversity and ecosystem functions. The present study underscores the importance of considering biotic interactions and adopting the metacommunity framework in conservation and restoration actions to support the management of freshwater ecosystems in an era of rapid global change. Read the free Plain Language Summary for this article on the Journal blog.

MetaIBM: A Python-based library for individual-based modelling of eco-evolutionary dynamics in spatial-explicit metacommunities

Individual-based modelling (IBM) is a powerful tool for simulating complex biological communities. By defining a population as comprising individuals that differ from one another, IBM can simulate the assembly and organisation of complex communities under various eco-evolutionary processes in a large spatial scale, with tremendous variables or parameters considered simultaneously. IBM disentangles a complex system into various sub-systems interacting with each other, allowing us to develop a unified library with a modular design for a wide range of complex scenarios in community assembly. In such a library, a number of parameters-controlled processes can be primitively coded as the sub-systems (or sub-models). Here, we released a Python-coded library as a framework for Metacommunity Individual-based Modelling (MetaIBM). As an open-source library, the MetaIBM has several merits, including: (a) it can be used to simulate a wide range of ecological problems of metacommunities. The metacommunity landscape and its environment gradients can be designed flexibly by users. Users can selectively turn off or on and set up parameters-controlled ecological processes according to their needs. (b) It adopts optimised algorithms and adapts to the high-performance computing devices, so that the users can explore a wide range of parameters space synchronously within a reasonable time. (c) It can be used to simulate a group of communities with up to millions of unique individuals, which is an originally plain portrayal of natural communities. To guide potential users, we provided the source codes of the library and a user manual. In the present article, we gave four examples to demonstrate how to design and model a metacommunity using the MetaIBM, simulating the community assembly in an islands-mainland model under the metacommunity framework with (a) neutral assumptions, (b) niche assumptions, (c) slow evolution scenarios, (d) rapid evolution scenarios. The examples showed that the MetaIBM can efficiently fit the community assembly, and reveal several intrigued species diversity patterns under the interaction of evolutionary processes and dispersal processes at multiple scales. The MetaIBM will be continuously maintained and updated to provide more functions in the future.

Identifying community assembling zones and connectivity pathways in the Tropical Southwestern Atlantic Ocean

Dispersal is more intense in the ocean than on land because most marine taxa present planktonic life stages that are transported by currents even without specific morphological traits. Thus, species dispersal shapes the distribution of biodiversity along seascapes and drives the composition of biodiversity assemblages. To identify marine assembling zones which characterise spatial areas particularly prone to receive and retain similar animal assemblages from the regional pool of species through passive dispersal, we propose a community‐based approach grounded on Lagrangian simulations of plankton dispersal. This novel approach was applied to communities (coast, outer shelf, slope, seamounts and islands; 0–80 m depth) of the Tropical Southwestern Atlantic and used to assess connectivity pathways. For that, we classified the modelled particles in 15 categories according to biological traits (planktonic life duration and spawning habitat) of representative planktonic communities. From the hierarchical clustering of the multivariate matrix containing the amount of arriving particles from each category in each cell we defined 14 assembling zones. Results highlighted that the assembling zones were mostly shaped by the degree of exposure to currents and the presence of mesoscale features (eddies, recirculation) derived from the interaction between these currents and coastlines. The boundaries, dispersal and connectivity patterns of these zones consistently align with local and regional in situ spatial distribution and abundance patterns of organisms, and provide an appropriate basis for the formulation of ecological hypotheses in the metacommunity framework to be tested in situ, such as the balance between species sorting and mass effect assembling archetypes. This approach, when coupled with the knowledge of other processes shaping communities' structure and distribution, provides important insights for regions and animal groups for which knowledge is limited or absent, and more generally allows for a comprehensive overview of the distribution of distinct communities and connectivity pathways along marine environments.

The influence of spatial processes on fish community structure: using a metacommunity framework for freshwater bioassessment.

The use of biological indicators in a bioassessment approach is important for inferences of anthropogenic stress in routine monitoring programs. One of the primary assumptions of bioassessment is that biological indicators observed at specific sampling sites will allow for inferences of local environmental quality; however, this assumption requires a reliable understanding of dispersal processes, which is particularly relevant in river systems due to their dendritic network. Inter-stream dispersal between different points of the river network could bias bioassessment, especially for highly mobile organisms like fish. Here, we examine standard biological metrics used in routine biomonitoring to determine how spatial variables, including dispersal, influence inferences between fish populations and environmental gradients. Using redundancy analysis (RDA) and variation partitioning, we tested the relative influence of both environmental and spatial variables on fish community structure and related community metrics. Fish were collected from 99 sampling sites distributed across 44 rivers and streams of the Great Morava River Basin, Serbia. Electroconductivity, the percentage of agricultural areas, dissolved oxygen, ammonia, and nitrate-nitrogen were found to be significant environmental variables, while ten spatial predictors from broad- to small-scales were found to influence fish community structure and community metrics. Our results suggest that contemporary dispersal among streams influences fish community composition, but that trait-based metrics are less sensitive than basic measures of diversity to spatial processes. Our results highlight the need for spatially independent sampling, as well as the need to consider dispersal-based processes in routine biomonitoring.

Drivers of the spatiotemporal patterns of the mangrove crab metacommunity in a tropical bay.

Revealing community patterns and driving forces is essential in community ecology and a prerequisite for effective management and conservation efforts. However, the mangrove ecosystem and its important fauna group such as the crabs, still lack multi-processes research under metacommunity framework, resulting in evidence and theorical application gaps. To fill these gaps, we selected China's most representative mangrove bay reserve in tropical zone as a stable experimental system and conducted a seasonal investigation (July 2020, October 2020, January 2021, and April 2021) of mangrove crabs. We performed a multi-approach analysis using both pattern-based and mechanistic method to distinguish the processes driving the mangrove crab metacommunity. Our results showed that the crab metacommunity exhibits a Clementsian pattern in the bay-wide mangrove ecosystem but is influenced by both local environmental heterogeneity and spatial processes, thus representing a combined paradigm of species sorting and mass effect. Moreover, the long-distance spatial constraints are more pronounced compared to the local environmental factors. This is reflected in the greater importance of the broad-scale Moran's Eigenvector Maps, the distance-decay pattern of similarity, and the difference in beta diversity dominated by the turnover component. This pattern changes throughout the year, mainly due to changes in dominant functional groups caused by the stress of changes in water salinity and temperature induced by air temperature and precipitation. This research provides multi-dimension research data and relevant analysis, offering clear evidence for understanding the patterns and related driving forces of crab metacommunity in tropical bay mangroves, and verifies the applicability of some general laws in the system. Future studies can address more diverse spatiotemporal scales, gaining a clearer understanding to serve the conservation of mangrove ecosystems and economically important fishery species.

Tourism affects microbial assemblages in show caves

Anthropogenic disturbance on natural ecosystems is growing in frequency and magnitude affecting all ecosystems components. Understanding the response of different types of biocoenosis to human disturbance is urgently needed and it can be achieved by adopting a metacommunity framework. With the aid of advanced molecular techniques, we investigated sediment communities of Fungi, Bacteria and Archaea in four Italian show caves, aiming to disentangle the effects induced by tourism on their diversity and to highlight changes in the driving forces that shape their community composition. We modelled diversity measures against proxies of tourism pressure. With this approach we demonstrate that the cave tourism has a direct effect on the community of Bacteria and an indirect influence on Fungi and Archaea. By analysing the main driving forces influencing the community composition of the three microbial groups, we highlighted that stochastic factors override dispersal-related processes and environmental selection in show caves compared to undisturbed areas. Thanks to this approach, we provide new perspectives on the dynamics of microbial communities under human disturbance suggesting that a proper understanding of the underlying selective mechanisms requires a comprehensive and multi-taxonomic approach.

Island biogeography at the mesoscale: Distance from forest edge affects choice of patch size by ovipositing treefrogs

Diversity in habitat patches is partly driven by variation in patch size, which affects extinction, and isolation, which affects immigration. Patch size also affects immigration as a component of patch quality. In wetland ecosystems, where variation in patch size and interpatch distance is ubiquitous, relationships between size and isolation may involve trade‐offs. We assayed treefrog oviposition at three patch sizes in arrays of two types, one where size increased with distance from forest (dispersed) and one with all patches equidistant from forest (equidistant), testing directly for an interaction between patch size and distance, which was highly significant. Medium patches in dispersed arrays received more eggs than those in equidistant arrays as use of typically preferred larger patches was reduced in dispersed arrays. Our results demonstrated a habitat selection trade‐off between preferred large and less‐preferred medium patches across small‐scale variation in isolation. Such patch size/isolation relationships are critical to community assembly and to understanding how diversity is maintained within a metapopulation and metacommunity framework, especially as wetland habitat becomes increasingly rare and fragmented. These results bring lessons of island biogeography, writ large, to bear on questions at small scales where ecologists often work and where habitat restoration is most often focused.

A patch-dynamic metacommunity perspective on the persistence of mutualistic and antagonistic bipartite networks.

The structure of interactions between species within a community plays a key role in maintaining biodiversity. Previous studies found that the effects of these structures might vary substantially depending on interaction type, for example, a highly connected and nested architecture stabilizes mutualistic communities, while the stability of antagonistic communities is enhanced in modular and weakly connected structures. Here we show that, when network dynamics are modeled using a patch-dynamic metacommunity framework, the qualitative differences between antagonistic and mutualistic systems disappear, with nestedness and modularity interacting to promote metacommunity persistence. However, the interactive effects are significantly weaker in antagonistic metacommunities. Our model also predicts an increase in connectance, nestedness, and modularity over time in both types of interaction, except in antagonistic networks, where nestedness declines. At steady state, we find a strong negative correlation between nestedness and modularity in both mutualistic and antagonistic metacommunities. These predictions are consistent with the structural trends found in a large data set of real-world antagonistic and mutualistic communities.

Competition-colonization dynamics and multimodality in diversity-disturbance relationships.

Disturbance has long been recognized as a critical driver of species diversity in community ecology. Recently, it has been found that the well-known intermediate disturbance hypothesis, which predicts a unimodal diversity-disturbance relationship (DDR), fails to describe numerous experimental observations, as empirical DDRs are diverse. Consequently, the precise form of the DDR remains a topic of debate. Here we develop a simple yet comprehensive metacommunity framework that can account for complex competition patterns. Using both numerical simulations and analytical arguments, we show that strongly multimodal DDRs arise naturally, and this multimodality is quite robust to changing parameters or relaxing the assumption of a strict competitive hierarchy. Having multimodality as a robust property of DDRs in competition models suggests that much of the noise observed in empirical DDRs could be a critical signature of the underlying competitive dynamics.

On the efficacy of restoration in stream networks: comments, critiques, and prospective recommendations

Swan and Brown (2017) recently addressed the effects of restoration on stream communities under the meta-community framework. Using a combination of headwater and mainstem streams, Swan and Brown (2017) evaluated how position within a stream network affected the outcome of restoration on invertebrate communities. Ostensibly, their hypotheses were partially supported as restoration had stronger effects in headwater streams: invertebrate taxonomic richness was increased and temporal variability decreased in restored reaches; however, these results were not consistent upon closer scrutiny for both the original paper (Swan and Brown 2017) and the later erratum (Swan and Brown 2018). Here, I provide a secondary analysis of the data, with hypotheses and interpretations in the context of stream, meta-community, and restoration ecology. Swan and Brown (2017, 2018) evaluated the effect of restoration on sites receiving various combinations of in-channel manipulation and riparian reforestation treatments. Given the difference in the relative importance of environmental filtering and dispersal between headwaters and mainstems and the structure of river networks, I contend that different restoration treatments have differential effects between headwaters and mainstems. I hypothesized in-channel manipulations would have more consistent effects between headwaters and mainstems compared to riparian reforestation, and I used this hypothesis to guide site selection in the re-analysis. I then compared results from the re-analysis to those presented by Swan and Brown (2017, 2018). I did not find any effects of restoration on local diversity, spatial dissimilarity, or temporal variability, let alone differential effects of restoration between headwaters and mainstems; these results are contrary Swan and Brown (2017, 2018), who reported that restoration increased taxonomic richness, increased spatial dissimilarity, and decreased temporal variability in restored headwater streams. I demonstrate further that the statistical tests conducted by Swan and Brown (2017, 2018) were invalid and, therefore, recommend the use of the results presented here. More broadly, I suggest, in agreement with Swan and Brown (2017, 2018) and a growing body of research, that river and stream restoration will likely have greater success if a regional approach is taken to designing and implementing restoration projects.

Culturable bacteria are more common than fungi in floral nectar and are more easily dispersed by thrips, a ubiquitous flower visitor.

Variation in dispersal ability among taxa affects community assembly and biodiversity maintenance within metacommunities. Although fungi and bacteria frequently coexist, their relative dispersal abilities are poorly understood. Nectar-inhabiting microbial communities affect plant reproduction and pollinator behavior, and are excellent models for studying dispersal of bacteria and fungi in a metacommunity framework. Here, we assay dispersal ability of common nectar bacteria and fungi in an insect-based dispersal experiment. We then compare these results with the incidence and abundance of culturable flower-inhabiting bacteria and fungi within naturally occurring flowers across two coflowering communities in California across two flowering seasons. Our microbial dispersal experiment demonstrates that bacteria disperse via thrips among artificial habitat patches more readily than fungi. In the field, incidence and abundance of culturable bacteria and fungi were positively correlated, but bacteria were much more widespread. These patterns suggest shared dispersal routes or habitat requirements among culturable bacteria and fungi, but differences in dispersal or colonization frequency by thrips, common flower visitors. The finding that culturable bacteria are more common among nectar sampled here, in part due to superior thrips-mediated dispersal, may have relevance for microbial life history, community assembly of microbes, and plant-pollinator interactions.

Partitioning and drivers of aquatic insect beta diversity in mountain streams

In recent years, interest in considering multiple facets of diversity has grown among community ecologists. Biological communities are complex systems, and exploring multiple facets can help reveal the main processes that drive diversity patterns. In this paper, we used a metacommunity framework to study the taxonomic, phylogenetic, and functional facets of beta diversity in assemblages of aquatic insects (Ephemeroptera and Trichoptera) with data from mountain streams collected in 2 study systems in the Mata Atlântica (Atlantic Forest) of Brazil: 22 streams from the northern coast of the São Paulo State and 33 streams from the southern coast of São Paulo State. We assessed the following: 1) the relative contributions of turnover and nestedness for different facets of beta diversity and 2) the relationships between environmental and spatial factors on the different facets and components of beta diversity. Beta diversities were high for all facets, and turnover was the main component of the taxonomic (based on incidence and abundance) and phylogenetic facets. In contrast, nestedness was an important component of the functional facet. The roles played by environmental and spatial variables varied erratically between the studied facets, insect orders, and study systems. Environment and space were both poor predictors of the different facets of beta diversity. Our results demonstrated that the difficulty of explaining the taxonomic beta diversity observed in other studies of aquatic insect stream metacommunities also arises for other facets of beta diversity (phylogenetic and functional). The high values of turnover found for most facets suggest that conservation strategies should seek to preserve as many streams as possible within a hydrographic network.

Connectivity of communities interacts with regional heterogeneity in driving species diversity: a mesocosm experiment

AbstractAccording to metacommunity theory and previous experiments, inter‐patch dispersal rates may alter species diversity at local to regional scales. In this study, we tested the predictions of metacommunity theory regarding the effect of dispersal rates on diversity, with a focus on the impact of environmental heterogeneity. Experiments were conducted in which the dispersal frequencies of freshwater nematode communities and the heterogeneity of local environmental conditions were factorial manipulated by maintaining mesocosms under homogeneous or heterogeneous temperature regime. The effect on biodiversity of the dispersal rate, environmental heterogeneity, and the interaction thereof were evaluated using linear (mixed) models, which showed a significant interaction of the dispersal rate and environmental heterogeneity for alpha‐ and gamma‐diversity measures. Specifically, in homogeneous environments an increase in the dispersal rates led to a decline in diversity at local and regional scales. This was due to the increasing dominance ofDaptonema dubium, which was favored by a higher patch connectivity that allowed it to invade local communities. In heterogeneous environments, diversity was unaffected, suggesting that rescue and source‐sink effects did not play a role for many species, probably due to the wide temperature range. Diversity was also not impacted by high and low dispersal treatments, and the maximum change was already reached at a dispersal rate of <7% in 4 weeks. The communities were then sampled a second time to investigate the development of diversity when dispersal and thus community connectivity are suspended. After only 12 weeks of isolation, the homogenizing effect of dispersal on community disappeared. The results point to the degree of environmental heterogeneity as key factor in the metacommunity framework. They also demonstrate the need to increase experimental complexity in order to facilitate comparisons between experiments.

Eutrophication increases deterministic processes and heterogeneity of co-occurrence networks of bacterioplankton metacommunity assembly at a regional scale in tropical coastal reservoirs

Understanding microbial metacommunity assembly and the underlying methanisms are fundamental objectives of aquatic ecology. However, little is known about how eutrophication, the primary water quality issue of aquatic ecosystems, regulates bacterioplankton metacommunity assembly at a regional scale in reservoirs. In this study, we applied a metacommunity framework to study bacterioplankton communities in 210 samples collected from 42 tropical coastal reservoirs in the wet summer season. We found that the spatial pattern of bacterioplankton community compositions (BCCs) at a regional scale was shaped mainly by species sorting. The reservoir trophic state index (TSI) was the key determinant of bacterioplankton metacommunity assembly. BCC turnover increased significantly with the TSI differences between sites (∆TSI) when ∆TSI was < 20, but remained at a level of about 80% when ∆TSI was > 20. Compared to oligo-mesotrophic and mesotrophic reservoirs, increased heterogeneity of co-occurrence bacterioplankton networks and bacterioplankton β-diversity were observed across eutrophic reservoirs. We propose that larger variation in phytoplankton community assembly may play directly or indirectly deterministic processes in controlling the bacterioplankton metacommunity assembly and became the potential mechanisms behind the observed higher BCC heterogeneity across the eutrophic reservoirs. Our research contributes to a broader understanding of the ecological effects of eutrophication on reservoir ecosystems and provides clues to the management of the tropical coastal reservoirs.

Fine‐scale functional metacommunity dynamics: Analysing the role of disturbance‐driven environmental variability in grasslands

AbstractQuestionPlant community dynamics are influenced by microvariations of the environment and of processes acting at fine spatio‐temporal scales like plant–plant interactions, local dispersal and phenology. However, descriptions and understanding of diversity changes both within year and over short distances are still required. We used a dynamic metacommunity framework to answer the following question: what is the relative influence of environmental filtering, dispersal limitation and ecological drift on fine‐scale grassland community dynamics under different disturbance regimes?LocationData were collected in a long‐term experiment located in the Massif Central, France (45°43′23″ N, 03°1′21″ E, 880 m a.s.l.).MethodsWe monitored fine‐scale spatio‐temporal community changes in small plots (i.e. local communities) distributed within six grassland paddocks (i.e. metacommunities) subject to two treatments (mown or grazed). We simultaneously monitored three key environmental variables: light, nitrogen and water, to assess how environmental heterogeneity impacts species compositional changes. We then inferred the metacommunity drivers of these changes in taxonomic and functional composition using a path analysis.ResultsManaged grasslands are dynamic within a year, and spatially heterogeneous within a paddock, with spatial and temporal β diversities totalling more than half of the taxonomic diversity. Mowing events caused sudden decreases of total vegetation cover resulting in taxonomical and functional changes. In grazed paddocks, community changes were mainly spatial due to spatially heterogeneous light‐structured filtering conditions. In both treatments, environmental heterogeneity only partially explained community changes that were also greatly impacted by dispersal limitation, but not ecological drift.ConclusionsOur study demonstrates that the fine‐scale analysis of community spatio‐temporal changes allows disentangling the relative importance of environmental filtering, dispersal limitation and ecological drift in community dynamics. Applying this approach to communities experiencing other kinds of disturbance regimes may allow gaining a general understanding of plant community assembly processes.

Evolutionary ecology of hydrothermal vent barnacles: Toward an understanding of the mechanisms underlying the biodiversity of deep-sea hydrothermal vent communities

Since the discovery of deep-sea hydrothermal vent communities in 1977, researchers have made efforts to understand the mechanisms underlying the biodiversity of these communities. “Biodiversity” is hierarchical in nature, ranging from genetic to ecosystem levels and local to regional scales, and encompassing genetic, species, ecosystem, and landscape diversity. A previous paper suggested that interactions between local and regional ecological processes in hydrothermal vent ecosystems could be understood through a metacommunity framework. As a first step toward understanding the complex interactions in these ecosystems, summarizing evolutionary-ecology studies conducted at different hierarchical levels for each vent taxon could be useful. Barnacles are suitable model species for studying evolutionary ecology at various spatiotemporal scales because of the good availability of fossil records, and because of their wide distribution and high potential for laboratory/field-based experiments using both larvae and adults. In this paper, studies on hydrothermal vent barnacles at each hierarchical level of biodiversity are reviewed.

From Marine Metacommunities to Meta-ecosystems: Examining the Nature, Scale and Significance of Resource Flows in Benthic Marine Environments

The metacommunity framework has been readily applied to coastal benthic marine environments to examine how larval dispersal affects the dynamics of patchily distributed communities. Transitioning to a meta-ecosystem perspective requires knowledge of interactions between living and non-living compartments occurring across scales in these environments. Here, we synthesize and analyze evidence of non-living resource flows in coastal benthic marine environments. Our objectives are to establish the types of benthic ecosystems that are coupled by resource flows, the spatial scale and directionality of the couplings, and the magnitude of resulting subsidization of recipient organisms. We find that resource flows commonly couple different types of coastal benthic ecosystems and can occur bidirectionally between ecosystems. Our quantitative synthesis yields a frequency distribution of resource flow distance, which suggests they frequently couple ecosystems across smaller distances than larval dispersal and that the probability of resource flows coupling benthic ecosystems decreases exponentially with distance between ecosystems. The magnitude of subsidization of recipient organisms also decreases with distance from the source of the resource flow. Our findings reveal that considering ecosystem heterogeneity and the respective scales of different types of spatial flows will be an important component of extending the marine metacommunity framework to meta-ecosystems. We propose an avenue for integrating ecosystem heterogeneity into meta-ecosystem theory, based upon general differences in functioning across coupled ecosystems revealed by our synthesis, and we argue for the development of a hierarchical meta-ecosystem theory.

Integrating Disturbance, Seasonality, Multi-Year Temporal Dynamics, and Dormancy Into the Dynamics and Conservation of Metacommunities

The metacommunity framework has rapidly become a dominant concept used by ecologists to understand community assembly. By emphasizing extinction-colonization dynamics, dispersal, and species’ niche requirements in determining community structure, metacommunity theory unifies local and regional processes as integral to species distributions across landscapes. Metacommunity structure has traditionally been treated as static. However, habitat characteristics and community composition can shift through time because of factors like seasonal dynamics, ecosystem disturbance, multi-year climate variation (e.g., El Niño Southern Oscillation), and production and emergence of dormant propagules. In most systems, the relevance of such temporal variation for the structure and persistence of metacommunities is an open question that is of potential importance for conservation and management. We evaluate and synthesize the theory and concepts relevant to four major forms of temporal dynamics that are pertinent to metacommunities: disturbance, seasonality, multi-year climate variation, and dormancy. For each type of dynamic we review the theoretical underpinnings and empirical evidence to evaluate how the dynamic drives temporal variation in metacommunity structure. We also consider how major forms of anthropogenic change further influence these patterns. Our survey highlights that seasonal climatic differences can modify the distribution and availability of resources and connectivity, with consequences for species’ use of the landscape and species interactions. Disturbance and multi-year climate cycles can increase the importance of dispersal, but implications for environmental filtering and species interactions remain unresolved. Dormant life stages serve to anchor habitat patches and species pools in space and highlight the importance of dispersal-dormancy tradeoffs and environmental variation for metacommunity structure. Temporal variability in biotic and abiotic conditions associated with these drivers can modify the relative strengths of dispersal, environmental filtering, and species interactions, three biological processes that drive metacommunity structure. Inclusion of spatiotemporal drivers creates patterns of species diversity that differ from traditional metacommunity ideas. We use these insights to highlight research needs, suggest a reconceptualization of metacommunities as undergoing continuous change, and discuss the implications of temporal dynamism for the conservation and management of metacommunities.

Large- and small-regional-scale variables interact in the dispersal patterns of aquatic macroinvertebrates from temporary ponds

Dispersal is one of the main determinants of metacommunity assembly, yet its interaction with the landscape network structure has not been fully elucidated. Large-scale regional factors such as the centrality–isolation gradient influence community abundance and richness, but small-scale regional factors, such as the direction or the distance among water bodies, might also influence them. Furthermore, the specific dispersal ability of each of the taxa will also determine this interaction. All these drivers are generally difficult to analyse together, but mesocosms usage combined with network analysis can help disentangle their relevance. We used these approaches to analyse how large and small regional factors influence dispersal dynamics. We set up several mesocosms around two source ponds with divergent locations within the network centrality–isolation gradient, at different distances and in different directions. We analysed macroinvertebrates composition and temporal trends throughout the hydroperiod considering the two regional factors: large (centrality–isolation gradient) and small (distance or direction separately) and dispersal ability (i.e. weak or strong). The large scale, being central or isolated, determined abundance and richness across the hydroperiod, with greater values in central locations. However, small regional factors, especially direction, modulated this trend making it similar to the central locations. Contrastingly, the small regional scales did not affect community composition, which differed along the large scale. Our results suggest that centrality–isolation plays a marked role in assembly processes favouring greater dispersal in central locations. However, this general pattern can be modulated by smaller regional factors and by intrinsic taxa dispersal ability, something that must be accounted within the metacommunity framework.

Environmental filtering and spillover explain multi-species edge responses across agricultural boundaries in a biosphere reserve

To ensure integrity of protected areas we need to understand how species respond to anthropogenic borders. We investigate, from a metacommunity perspective, the direct and indirect mechanisms by which transformed areas affect distribution patterns of ground-living arthropod assemblages inhabiting an extensive protected area adjacent to fruit orchards in an important biosphere reserve. Arthropods and environmental variables were sampled along transects perpendicular to natural-orchard edges. Influence of distance from orchard boundary, degree of impermeability of the boundary, orchard habitat quality (local scale land-use intensity), and edge-induced changes in local environmental variables on arthropod species richness and composition in non-crop habitats were assessed. Arthropod groups were assessed in terms of habitat fidelity: species associated with natural habitat (stenotopic species), those within crop habitat (cultural species), and those showing no preference for either habitat (ubiquitous species). Spillover resulted in higher cultural species richness near edges, but not higher overall species richness. Environmental filtering was important for stenotopic species composition, which was influenced by edge-induced changes in environmental variables. Ubiquitous species composition was determined by orchard impermeability. Increased orchard habitat quality was associated with higher cultural and ubiquitous species richness. The effects of orchards on assemblages in natural habitats can be variable, but predictable when using species habitat specificity in conjunction with a metacommunity framework. High intensity orchards may act as sink habitats, especially for species that readily disperse between crop and natural habitats. Here we recommend that local buffer strips are > 85 m wide, which will reduce the influence of cultural species spillover on sensitive natural ecosystems.