Dispersal restricts local biomass but promotes the recovery of metacommunities after temperature stress

Landscape connectivity can increase the capacity of communities to maintain their function when environments change by promoting the immigration of species or populations with adapted traits. However, high immigration may also restrict fine tuning of species compositions to local environmental conditions by homogenizing the community. Here we demonstrate that dispersal generates such a tradeoff between maximizing local biomass and the capacity of model periphyton metacommunities to recover after a simulated heat wave. In non‐disturbed metacommunities, dispersal decreased the total biomass by preventing differentiation in species composition between the local patches making up the metacommunity. On the contrary, in metacommunities exposed to a realistic summer heat wave, dispersal promoted recovery by increasing the biomass of heat tolerant species in all local patches. Thus, the heat wave reorganized the species composition of the metacommunities and after an initial decrease in total biomass by 38.7%, dispersal fueled a full recovery of biomass in the restructured metacommunities. Although dispersal may decrease equilibrium biomass, our results highlight that connectivity is a key requirement for the response diversity that allows ecological communities to adapt to climate change through species sorting.     

Effect of (a)synchronous light fluctuation on diversity,functional and structural stability of a marine phytoplankton metacommunity

Disentangling the mechanisms that maintain the stability of communities and ecosystem properties has become a major research focus in ecology in the face of anthropogenic environmental change. Dispersal plays a pivotal role in maintaining diversity in spatially subdivided communities, but only a few experiments have simultaneously investigated how dispersal and environmental fluctuation affect community dynamics and ecosystem stability. We performed an experimental study using marine phytoplankton species as model organisms to test these mechanisms in a metacommunity context. We established three levels of dispersal and exposed the phytoplankton to fluctuating light levels, where fluctuations were either spatially asynchronous or synchronous across patches of the metacommunity. Dispersal had no effect on diversity and ecosystem function (biomass), while light fluctuations affected both evenness and community biomass. The temporal variability of community biomass was reduced by fluctuating light and temporal beta diversity was influenced interactively by dispersal and fluctuation, whereas spatial variability in community biomass and beta diversity were barely affected by treatments. Along the establishing gradient of species richness and dominance, community biomass increased but temporal variability of biomass decreased, thus highest stability was associated with species-rich but highly uneven communities and less influenced by compensatory dynamics. In conclusion, both specific traits (dominance) and diversity (richness) affected the stability of metacommunities under fluctuating conditions.     

The influence of dispersal on the realized trajectory of a pond metacommunity

Dispersal rates play a critical role in metacommunity dynamics, yet few studies have attempted to characterize dispersal rates for the majority of species in any natural community. Here we evaluate the relationship between the abundances of 179 plankton taxa in a pond metacommunity and their dispersal rates. We find the expected positive relationship between the regional abundances of phytoplankton, protozoa and metazoan zooplankton, which is suggestive of dispersal being a density‐independent per capita rate for these groups. When we tested to see if the rates of dispersing taxa predicted changes in community composition, we found that dispersers had no measurable impact on the short‐term trajectory of local pond communities or mesocosm communities established experimentally (assembled communities), but became increasingly represented in the overall pond metacommunity during the course of the full growing season. In comparison, the composition of experimental mesocosms that lacked any initial zooplankton community (unassembled communities) were found to be driven by dispersal measured at the local pond community but not by dispersal observed across the overall metacommunity. These results suggest that the role of dispersal may shift from a contributor to local, ecological dynamics to that of metacommunity‐wide, colonization–extinction dynamics as communities assemble.     

Warming induces synchrony and destabilizes experimental pond zooplankton metacommunities

The spatial insurance hypothesis predicts that intermediate rates of dispersal between patches in a metacommunity allow species to track favourable conditions, preserving diversity and stabilizing biomass at local and regional scales. However, theory is unclear as to whether dispersal will provide spatial insurance when environmental conditions are changing directionally. In particular, increased temperatures as a result of climate change are expected to cause synchronous growth or decline across species and communities, and this has the potential to erode the stabilizing compensatory dynamics facilitated by dispersal. Here we report on an experimental test of how dispersal affects the diversity and stability of metacommunities under warming using replicate two‐patch pond zooplankton metacommunities. Initial differences in local community composition and abiotic conditions were established by seeding each patch in the metacommunities with plankton and sediment from one of two natural ponds that differed in water chemistry and species composition. We exposed metacommunities to a 2°C increase in average ambient temperature, crossed with three rates of dispersal (none, intermediate, high). In ambient conditions, intermediate dispersal rates preserved diversity and stabilized metacommunities by promoting spatially asynchronous fluctuations in biomass, especially between local populations of the dominant genus, Ceriodaphnia. However, warming synchronized their populations so that these effects of dispersal were lost. Furthermore, because the stabilizing effect of dispersal was primarily due to asynchronous fluctuations between populations of a single genus, metacommunity biomass was stabilized, but dispersal did not stabilize local community biomass. Our results show that dispersal can preserve diversity and provide stability to metacommunities, but also show that this benefit can be eroded when warming is directional and synchronous across patches of a metacommunity, as is expected with climate warming.     

Using functional diversity patterns to explore metacommunity dynamics: a framework for understanding local and regional influences on community structure

The metacommunity concept, describing how local and regional scale processes interact to structure communities, has been successfully applied to patterns of taxonomic diversity. Functional diversity has proved useful for understanding local scale processes, but has less often been applied to understanding regional scale processes. Here, we explore functional diversity patterns within a metacommunity context to help elucidate how local and regional scale processes influence community assembly. We detail how each of the four metacommunity perspectives (species sorting, mass effects, patch dynamics, neutral) predict different patterns of functional beta‐ and alpha‐diversity and spatial structure along two key gradients: dispersal limitation and environmental conditions. We then apply this conceptual model to a case study from alpine tundra plant communities. We sampled species composition in 17 ‘sky islands’ of alpine tundra in the Colorado Rocky Mountains, USA that differed in geographic isolation and area (key factors related to dispersal limitation) and temperature and elevation (key environmental factors). We quantified functional diversity in each site based on specific leaf area, leaf area, stomatal conductance, plant height and chlorophyll content. We found that colder high elevation sites were functionally more similar to each other (decreased functional beta‐diversity) and had lower functional alpha‐diversity. Geographic isolation and area did not influence functional beta‐ or alpha‐diversity. These results suggest a strong role for environmental conditions structuring alpine plant communities, patterns consistent with the species sorting metacommunity perspective. Incorporating functional diversity into metacommunity theory can help elucidate how local and regional factors structure communities and provide a framework for observationally examining the role of metacommunity dynamics in systems where experimental approaches are less tractable.     

Metacommunity size influences aquatic community composition in a natural mesocosm landscape

Ecosystems are often arranged in naturally patchy landscapes with habitat patches linked by dispersal of species in a metacommunity. The size of a metacommunity, or number of patches, is predicted to influence community dynamics and therefore the structure and function of local communities. However, such predictions have yet to be experimentally tested using full food webs in natural metacommunities. We used the natural mesocosm system of aquatic macroinvertebrates in bromeliad phytotelmata to test the effect of the number of patches in a metacommunity on species richness, abundance, and community composition. We created metacommunities of varying size using fine mesh cages to enclose a gradient from a single bromeliad up to the full forest. We found that species richness, abundance, and biomass increased from enclosed metacommunities to the full forest size and that diversity and evenness also increased in larger enclosures. Community composition was affected by metacommunity size across the full gradient, with a more even detritivore community in larger metacommunities, and taxonomic groups such as mosquitoes going locally extinct in smaller metacommunities. We were able to divide the effects of metacommunity size into aquatic and terrestrial habitat components and found that the importance of each varied by species; those with simple life cycles were only affected by local aquatic habitat whereas insects with complex life cycles were also affected by the amount of terrestrial matrix. This differential survival of obligate and non‐obligate dispersers allowed us to partition the beta‐diversity between metacommunities among functional groups. Our study is one of the first tests of metacommunity size in a natural metacommunity landscape and shows that both diversity and community composition are significantly affected by metacommunity size. Synthesis Natural food webs are sensitive to meta‐community size, i.e. the number of patches connected through dispersal. We provide an empirical test using the aquatic foodweb associated within bromeliads as a model system. When we reduced the number of bromeliad patches connect through dispersal, we found a clear change of the foodweb in terms of population sizes, beta diversity, community composition and predator‐prey ratios. The response of individual taxa was predictable based on species traits including dispersal modes, life cycle, and adult resource requirements. Our study demonstrates that community structure is strongly influenced by the interplay of species traits and landscape properties.     

Disentangling the effects of local and regional processes on biodiversity patterns through taxon‐contingent metacommunity network analysis

Metacommunity theory, which has gained a central position in ecology, accounts for the role of migration in patterns of diversity among communities at different scales. Community isolation has a main role in this theory, but is difficult to estimate empirically, partly due to the taxon‐dependent nature of dispersal. Landscapes could be perceived as either fragmented or connected for organisms with contrasting dispersal abilities. Indeed, the dispersal ability of a taxon, and the spatial scale at which eco‐evolutionary processes shape local diversity, determine a taxon‐dependent metacommunity network. In this paper, we introduce a methodology using graph theory to define this taxon‐dependent metacommunity network and then to estimate the isolation of local communities. We analyzed the relative importance of local conditions versus community isolation as determinants of community richness for 25 taxa inhabiting 18 temporary ponds. Although local factors have been the foci of most previous empirical and theoretical considerations, we demonstrate that the metacommunity network is an equally important contributor to local diversity. We also found that the relative effect of local conditions and the metacommunity network depend on body size and taxon abundance. Local diversity of larger species was more affected by patch isolation, while taxon abundances were associated with positive or negative effects of isolation. Our results provide empirical support for the proposed role of metacommunity networks as determinants of community diversity and show the taxon‐dependent nature of these networks.     

Dispersal among local communities does not reduce historical contingencies during metacommunity assembly

Ample evidence suggests that ecological communities can exhibit historical contingencies. However, few studies have explored whether differences in assembly history can generate alternative local community states in metacommunities in which local communities are linked by dispersal. In a protist microcosm experiment, we examined the influence of species colonization history on metacommunity assembly under homogeneous environmental conditions, by manipulating both the sequence of species colonization into local communities and the rate of dispersal among local communities. Whereas the role of dispersal in structuring local communities decreased over time and became non‐significant towards the end of the experiment, species colonization history significantly influenced local communities throughout the experiment. Local communities, regardless of the rate of dispersal among them, exhibited two alternative states characterized by the dominance of different species. The alternative community states, however, emerged in the absence of priority effects that were often associated with alternative community states found in other assembly studies. Rather, they were driven by variation in species interaction strength among local communities with different assembly histories. These results suggest that dispersal among local communities may not necessarily reduce the role of species colonization history in shaping metacommunity assembly, and that differences in species colonization history need to be explicitly considered as an important factor in causing heterogeneous community states in metacommunities.     

Dispersal rates affect species composition in metacommunities of Sarracenia purpurea inquilines

Dispersal among local communities can have a variety of effects on species composition and diversity at local and regional scales. Local conditions (e.g., resource and predator densities) can have independent effects, as well as interact with dispersal, to alter these patterns. Based on metacommunity models, we predicted that local diversity would show a unimodal relationship with dispersal frequency. We manipulated dispersal frequencies, resource levels, and the presence of predators (mosquito larvae) among communities found in the water-filled leaves of the pitcher plant Sarracenia purpurea. Diversity and abundance of species of the middle trophic level, protozoa and rotifers, were measured. Increased dispersal frequencies significantly increased regional species richness and protozoan abundance while decreasing the variance among local communities. Dispersal frequency interacted with predation at the local community scale to produce patterns of diversity consistent with the model. When predators were absent, we found a unimodal relationship between dispersal frequency and diversity, and when predators were present, there was a flat relationship. Intermediate dispersal frequencies maintained some species in the inquiline communities by offsetting extinction rates. Local community composition and the degree of connectivity between communities are both important for understanding species diversity patterns at local and regional scales.     

Primates create seedling growth hotspots through pattern of dung deposition

Primates play important roles in tropical forests through seed dispersal and herbivory. They comprise a large part of the biomass of forest communities and tend to have clumped patterns of defecations (i.e. at favoured food trees or sleeping sites). Therefore, they may also play important roles in accelerating ecosystem nutrient cycling. Here we conduct a controlled growth experiment to quantify the effect of the addition of primate dung on the growth of both light‐demanding and shade‐tolerant seedlings over 1 year in Kibale National Park, Uganda. A mixed model analysis revealed that light‐demanding species were affected by the natural dung treatment and plants with small initial size had accelerated growth, whereas there was no effect on plant growth for shade‐tolerant species. The long‐term implications of increased dung deposition on the local tree community are unclear as shade‐tolerant species may only show an effect over the long‐term and light‐demanding species may only be able to take advantage of the increased growth if subsequently exposed to high light conditions, such as a treefall gap.     

Combined effects of zooplankton grazing and dispersal on the diversity and assembly mechanisms of bacterial metacommunities

Effects of dispersal and the presence of predators on diversity, assembly and functioning of bacterial communities are well studied in isolation. In reality, however, dispersal and trophic interactions act simultaneously and can therefore have combined effects, which are poorly investigated. We performed an experiment with aquatic metacommunities consisting of three environmentally different patches and manipulated dispersal rates among them as well as the presence or absence of the keystone species Daphnia magna. Daphnia magna reduced both local and regional diversity, whereas dispersal increased local diversity but decreased beta‐diversity having no net effect on regional diversity. Dispersal modified the assembly mechanisms of bacterial communities by increasing the degree of determinism. Additionally, the combination of the D. magna and dispersal increased the importance of deterministic processes, presumably because predator‐tolerant taxa were spread in the metacommunity via dispersal. Moreover, the presence of D. magna affected community composition, increased community respiration rates but did not affect bacterial production or abundance, whereas dispersal slightly increased bacterial production. In conclusion, our study suggests that predation by a keystone species such as D. magna and dispersal additively influence bacterial diversity, assembly processes and ecosystem functioning.     

A heatwave increases turnover and regional dominance in microbenthic metacommunities

While the effect of the global biodiversity crisis on local species loss is still debated, there is empirical evidence for major changes in local biodiversity attributed to increased species turnover. In communities exposed to a climate stressor, species turnover can lead to increased dominance of well-adapted species and consequently to an overall decline in species diversity. Despite the known importance of species turnover for community dynamics and functioning, experimental results on the connection between biodiversity loss and species turnover are scarce. We still do not fully understand which specific factors increase the rate of change in species composition, especially when considering natural compared to artificially lab assembled communities. In the present study, we experimentally tested whether a heatwave and dispersal increased species turnover and decreased species diversity in natural benthic diatom communities with different initial species compositions. We found that on the local scale, dispersal had overall positive effects on species richness while the relationship between exposure to the heatwave, species turnover, and diversity depended on initial community composition. However, on the regional (i.e. metacommunity) scale, exposure to the heatwave and dispersal both increased turnover and decreased Shannon diversity by almost 50%. Turnover in these metacommunities was not caused by a loss of species, but rather by a change in dominance patterns leading to homogenization, and consequently decreased diversity. Our study shows that climate change can destabilize community composition and degrade species diversity, but still after ca. 15 generations does not decrease the number of species in the community, demonstrating that the response of species diversity and richness to changing conditions can be fundamentally decoupled on ecological time scales.     

Modularity along organism dispersal gradients challenges a prevailing view of abrupt transitions in animal landscape perception

A common property of landscapes and metacommunities is the occurrence of abrupt shifts in connectivity along gradients of individual dispersal abilities. Animals with short‐range dispersal capability perceive fragmented landscapes, but organisms moving across critical thresholds perceive continuous landscapes. This qualitative shift in landscape perception may determine several attributes of local communities and the dynamics of whole metacommunities. Modularity describes the existence in some communities of relatively high numbers of mutual connections favoring the movement of neighboring individuals (even when each individual is able to reach any patch in the landscape). Local patch linkages and metacommunity connectivity along gradients of dispersal ability have been reported frequently. However, the intermediate level of structure captured by modularity has not been considered. We evaluated landscape connectivity and modularity along gradients of individual dispersal abilities. Random landscapes with different degrees of cell aggregation and occupancy were simulated; we also analyzed ten real ecosystems. An expected, a shift in landscape connectivity was always detected; modularity consistently decreased gradually along dispersal gradients in both simulated networks and empirical landscapes. Neutral metacommunities within simulated landscapes demonstrated that modularity and connectivity may reflect landscape traits in the shaping of metacommunity diversity. Average beta‐diversity was strongly associated with modularity, particularly with low migration rates, while connectivity trends tracked changes in beta‐diversity at intermediate to high migrations rates. Consequently, while some species are able to perceive abrupt transitions in the landscape, many others probably experience a gradual continuum in landscape perception, contrary to predictions from previous analyses. Furthermore, the gradual behavior of modularity indicates that it may represent an exceptional early‐warning tool that measures system distance to tipping points. Our study highlights the multiple perceptions that different species may have of a single landscape and shows, for the first time, a theoretical and empirical relationship between landscape modularity, and metacommunity diversity.     

The importance of landscape and habitat properties in explaining instantaneous and long‐term distributions of large branchiopods in subtropical temporary pans

1. The notion that the spatial configuration of habitat patches has to be taken into account to understand the structure and dynamics of ecological communities is the starting point of metacommunity ecology. One way to assess metacommunity structure is to investigate the relative importance of environmental heterogeneity and spatial structure in explaining community patterns over different spatial and temporal scales. 2. We studied metacommunity structure of large branchiopod assemblages characteristic of subtropical temporary pans in SE Zimbabwe using two community data sets: a community snapshot and a long‐term data set covering 4 years. We assessed the relative importance of environmental heterogeneity and dispersal (inferred from patch occupancy patterns) as drivers of community structure. Furthermore, we contrasted metacommunity patterns in pans that occasionally connect to the river (floodplain pans) and pans that lack such connections altogether (endorheic pans) using redundancy models. 3. Echoes of species sorting and dispersal limitation emerge from our data set, suggesting that both local and regional processes contribute to explaining branchiopod assemblages in this system. Relative importance of local and regional factors depended on the type of data set considered. Overall, habitat characteristics that vary in time, such as conductivity, hydroperiod and vegetation cover, best explained the instantaneous species composition observed during a snapshot sampling while long‐term species composition appeared to be linked to more constant intrinsic habitat properties such as river connectivity and spatial location.     

Community differentiation on landscapes: drift, migration and speciation

Theories of the differentiation of ecological communities on landscapes have typically not considered evolutionary dynamics. Here we analytically study the expected differentiation among local communities in a large metacommunity, undergoing speciation, ecological drift and intercommunity dispersal, in the context of neutral theory. We demonstrate that heterogeneity in species diversity and abundance arises among communities when local communities are small and intercommunity migration is infrequent. We propose a new measure to describe community differentiation, defined as the average correlation or the average probability (C_st) that two randomly sampled individuals of the same species within local communities are from the same ancestor. The effects of driving forces (migration, mutation, and ecological drift) are incorporated into the two-level hierarchical community structure in a finite island model of neutral communities. Community differentiation can increase the effective metacommunity size or the Hubbell's fundamental species diversity in the metacommunity by a factor (1−C_st)⁻¹. Significant community differentiation arises when C_st≠0. Intercommunity migration promotes species diversity in local communities but reduce species diversity in the metacommunity. In either the finite or infinite island case, one can estimate the number of intercommunity migrants by using multiple local community datasets when the speciation is negligible in the neutral local communities, or by using the metacommunity dataset when the speciation is included in the local neutral communities. These results highlight the significance of the evolutionary mechanisms in generating heterogeneous communities in the absence of complicated ecological processes on large landscapes.     

Integrating internal and external dispersal in metacommunity assembly: preliminary theoretical analyses

Internal dispersal, which occurs among local communities within a metacommunity, and external dispersal, which supplies immigrants from outside the metacommunity, can both have a major impact on species diversity. However, few studies have considered the two simultaneously. Here I report preliminary computer-simulation results to suggest that internal and external dispersal can interact to influence species richness. Specifically, the results show that internal dispersal did not affect species richness under frequent external dispersal, whereas it enhanced richness in local communities while decreasing richness in metacommunities under infrequent external dispersal. Conversely, external dispersal influenced species richness in local communities more greatly in the absence of internal dispersal than in its presence, while external dispersal did not affect richness in metacommunities regardless of internal dispersal. Furthermore, internal and external dispersal interactively determined the importance of community assembly history in generating and maintaining variation in local community structure. Overall, these results suggest that the two dispersal types can reciprocally provide the context in which each affects species diversity and therefore that their effects cannot be understood in isolation of the other.Electronic Supplementary Material Supplementary material is available for this article at Tadashi Fukami is the recipient of the ninth Denzaburo Miyadi Award.     

Metacommunity speciation models and their implications for diversification theory

The emergence of new frameworks combining evolutionary and ecological dynamics in communities opens new perspectives on the study of speciation. By acknowledging the relative contribution of local and regional dynamics in shaping the complexity of ecological communities, metacommunity theory sheds a new light on the mechanisms underlying the emergence of species. Three integrative frameworks have been proposed, involving neutral dynamics, niche theory, and life history trade‐offs respectively. Here, we review these frameworks of metacommunity theory to emphasise that: (1) studies on speciation and community ecology have converged towards similar general principles by acknowledging the central role of dispersal in metacommunities dynamics, (2) considering the conditions of emergence and maintenance of new species in communities has given rise to new models of speciation embedded in the metacommunity theory, (3) studies of diversification have shifted from relating phylogenetic patterns to landscapes spatial and ecological characteristics towards integrative approaches that explicitly consider speciation in a mechanistic ecological framework. We highlight several challenges, in particular the need for a better integration of the eco‐evolutionary consequences of dispersal and the need to increase our understanding on the relative rates of evolutionary and ecological changes in communities.     

General relationships between consumer dispersal,resource dispersal and metacommunity diversity

One of the central questions of metacommunity theory is how dispersal of organisms affects species diversity. Here, we show that the diversity–dispersal relationship should not be studied in isolation of other abiotic and biotic flows in the metacommunity. We study a mechanistic metacommunity model in which consumer species compete for an abiotic or biotic resource. We consider both consumer species specialised to a habitat patch, and generalist species capable of using the resource throughout the metacommunity. We present analytical results for different limiting values of consumer dispersal and resource dispersal, and complement these results with simulations for intermediate dispersal values. Our analysis reveals generic patterns for the combined effects of consumer and resource dispersal on the metacommunity diversity of consumer species, and shows that hump‐shaped relationships between local diversity and dispersal are not universal. Diversity–dispersal relationships can also be monotonically increasing or multimodal. Our work is a new step towards a general theory of metacommunity diversity integrating dispersal at multiple trophic levels.     

Temporal dynamics of a local fish community are strongly affected by immigration from the surrounding metacommunity

A 5‐year time series of annual censuses was collected from a large floodplain lake to determine how dynamics of the local fish community were affected by changes in hydrological connectivity with the surrounding metacommunity. The lake was disconnected from the metacommunity for 1 year prior to our study and remained disconnected until 3 months before our third annual census, when a flood reconnected the lake to the metacommunity. We determined how changes in connectivity affected temporal dynamics of (1) local community composition and (2) the population composition, condition, and growth of catfish, to shed light on how immigration of other species might affect local population dynamics. Before reconnection, the community was likely shaped by interactions between the local environment and species traits. The reconnection caused significant immigration and change in community composition and correlated with a significant and abrupt decline in catfish condition, growth, and abundance; effects likely due to the immigration of a competitor with a similar trophic niche: carp. The community was slow to return to its preconnection state, which may be due to dispersal traits of the fishes, and a time‐lag in the recovery of the local catfish population following transient intensification of species interactions. The dynamics observed were concordant with the species sorting and mass‐effects perspectives of metacommunity theory. Floods cause episodic dispersal in floodplain fish metacommunities, and so, flood frequency determines the relative importance of regional and local processes. Local processes may be particularly important to certain species, but these species may need sufficient time between floods for population increase, before the next flood‐induced dispersal episode brings competitors and predators that might cause population decline. Accordingly, species coexistence in these metacommunities may be facilitated by spatiotemporal storage effects, which may in turn be regulated by flood frequency.     

Inferring species roles in metacommunity structure from species co-occurrence networks

A long-standing question in community ecology is what determines the identity of species that coexist across local communities or metacommunity assembly. To shed light upon this question, we used a network approach to analyse the drivers of species co-occurrence patterns. In particular, we focus on the potential roles of body size and trophic status as determinants of metacommunity cohesion because of their link to resource use and dispersal ability. Small-sized individuals at low-trophic levels, and with limited dispersal potential, are expected to form highly linked subgroups, whereas large-size individuals at higher trophic positions, and with good dispersal potential, will foster the spatial coupling of subgroups and the cohesion of the whole metacommunity. By using modularity analysis, we identified six modules of species with similar responses to ecological conditions and high co-occurrence across local communities. Most species either co-occur with species from a single module or are connectors of the whole network. Among the latter are carnivorous species of intermediate body size, which by virtue of their high incidence provide connectivity to otherwise isolated communities playing the role of spatial couplers. Our study also demonstrates that the incorporation of network tools to the analysis of metacommunity ecology can help unveil the mechanisms underlying patterns and processes in metacommunity assembly.