Metacommunity Dynamics Research Articles

Disentangling local, metapopulation, and cross-community sources of stabilization and asynchrony in metacommunities.

Asynchronous fluctuations of populations are essential for maintaining stable levels of bio-mass and ecosystem function in landscapes. Yet, understanding the stabilization of metacommunities by asynchrony is complicated by the existence of multiple forms of asynchrony that are typically studied independently: Community ecologists, for instance, focus on asynchrony within and among local communities, while population ecologists emphasize asynchrony of populations in metapopulations. Still, other forms of asynchrony, such as that which underlies the spatial insurance effect, are not captured by any existing analytical frameworks. We therefore developed a framework that would in one analysis unmask the stabilizing roles of local communities and metapopulations and so unify these perspectives. Our framework shows that metacommunity stabilization arises from one local and two regional forms of asynchrony: (1) asynchrony among species of a local community, (2) asynchrony among populations of a metapopulation, and (3) cross-community asynchrony, which is between different species in different local communities and underlies spatial insurance. For each type of stabilization, we derived links to diversity indices and associated diversity-stability relationships. We deployed this framework in a set of rock pool invertebrate metacommunities in Discovery Bay, Jamaica, to partition sources of stabilization and test their dependence on diversity. Cross-community asynchrony was the dominant form of stabilization, accounting for >60% of total metacommunity stabilization despite being undetectable with existing frameworks. Environmental variation influenced types of stabilization through different mechanisms. pH and dissolved oxygen, for example, increased asynchrony by decorrelating local species, while salinity did so by changing the abundance structure of metapopulations. Lastly, all types of asynchrony depended strongly on different types of diversity (alpha, metapopulation, and beta diversity drove local, metapopulation, and cross-community asynchrony, respectively) to produce multiple diversity-stability relationships within metacommunities. Our new partition of metacommunity dynamics highlights how different elements—from local communities to metapopulations—combine to stabilize metacommunities and depend critically on contrasting environmental regimes and diversities. Understanding and balancing these sources of stability in dynamic landscapes is a looming challenge for the future. We suggest that synthetic frameworks which merge ecological perspectives will be essential for grasping and safeguarding the stability of natural systems.

DNA metabarcoding reveals metacommunity dynamics in a threatened boreal wetland wilderness

The complexity and natural variability of ecosystems present a challenge for reliable detection of change due to anthropogenic influences. This issue is exacerbated by necessary trade-offs that reduce the quality and resolution of survey data for assessments at large scales. The Peace-Athabasca Delta (PAD) is a large inland wetland complex in northern Alberta, Canada. Despite its geographic isolation, the PAD is threatened by encroachment of oil sands mining in the Athabasca watershed and hydroelectric dams in the Peace watershed. Methods capable of reliably detecting changes in ecosystem health are needed to evaluate and manage risks. Between 2011 and 2016, aquatic macroinvertebrates were sampled across a gradient of wetland flood frequency, applying both microscope-based morphological identification and DNA metabarcoding. By using multispecies occupancy models, we demonstrate that DNA metabarcoding detected a much broader range of taxa and more taxa per sample compared to traditional morphological identification and was essential to identifying significant responses to flood and thermal regimes. We show that family-level occupancy masks high variation among genera and quantify the bias of barcoding primers on the probability of detection in a natural community. Interestingly, patterns of community assembly were nearly random, suggesting a strong role of stochasticity in the dynamics of the metacommunity. This variability seriously compromises effective monitoring at local scales but also reflects resilience to hydrological and thermal variability. Nevertheless, simulations showed the greater efficiency of metabarcoding, particularly at a finer taxonomic resolution, provided the statistical power needed to detect change at the landscape scale.

The Community Simulator: A Python package for microbial ecology.

Natural microbial communities contain hundreds to thousands of interacting species. For this reason, computational simulations are playing an increasingly important role in microbial ecology. In this manuscript, we present a new open-source, freely available Python package called Community Simulator for simulating microbial population dynamics in a reproducible, transparent and scalable way. The Community Simulator includes five major elements: tools for preparing the initial states and environmental conditions for a set of samples, automatic generation of dynamical equations based on a dictionary of modeling assumptions, random parameter sampling with tunable levels of metabolic and taxonomic structure, parallel integration of the dynamical equations, and support for metacommunity dynamics with migration between samples. To significantly speed up simulations using Community Simulator, our Python package implements a new Expectation-Maximization (EM) algorithm for finding equilibrium states of community dynamics that exploits a recently discovered duality between ecological dynamics and convex optimization. We present data showing that this EM algorithm improves performance by between one and two orders compared to direct numerical integration of the corresponding ordinary differential equations. We conclude by listing several recent applications of the Community Simulator to problems in microbial ecology, and discussing possible extensions of the package for directly analyzing microbiome compositional data.

Metacommunity Structure of Stream Insects across Three Hierarchical Spatial scales.

A major challenge in community ecology is to understand the underlying factors driving metacommunity (i.e., a set of local communities connected through species dispersal) dynamics. However, little is known about the effects of varying spatial scale on the relative importance of environmental and spatial (i.e., dispersal related) factors in shaping metacommunities and on the relevance of different dispersal pathways. Using a hierarchy of insect metacommunities at three spatial scales (a small, within‐stream scale, intermediate, among‐stream scale, and large, among‐sub‐basin scale), we assessed whether the relative importance of environmental and spatial factors shaping metacommunity structure varies predictably across spatial scales, and tested how the importance of different dispersal routes vary across spatial scales. We also studied if different dispersal ability groups differ in the balance between environmental and spatial control. Variation partitioning showed that environmental factors relative to spatial factors were more important for community composition at the within‐stream scale. In contrast, spatial factors (i.e., eigenvectors from Moran's eigenvector maps) relative to environmental factors were more important at the among‐sub‐basin scale. These results indicate that environmental filtering is likely to be more important at the smallest scale with highest connectivity, while dispersal limitation seems to be more important at the largest scale with lowest connectivity. Community variation at the among‐stream and among‐sub‐basin scales were strongly explained by geographical and topographical distances, indicating that overland pathways might be the main dispersal route at the larger scales among more isolated sites. The relative effect of environmental and spatial factors on insect communities varied between low and high dispersal ability groups; this variation was inconsistent among three hierarchical scales. In sum, our study indicates that spatial scale, connectivity, and dispersal ability jointly shape stream metacommunities.

Dispersal drives changes in fish community abundance in intermittent stream networks

AbstractIncreasing trends in fragmentation and dewatering of streams warrants research on how populations and communities respond to varying water levels and barriers to movement. Although these responses are complicated by many spatial and temporal processes, long‐term datasets might help reveal complex patterns and processes driving variability in species abundances. The objective of this study was to develop a predictive framework for fish community and population responses to varying levels of water availability across six sites in two intermittent stream networks sampled >10 years. We predicted that fishes would emigrate into intermittent reaches during wet conditions; thus, overall abundances within perennial source locations will decline. Accordingly, when intermittent reaches dry, fishes will contract to wetted habitats resulting in high abundance. Observed fish community abundances were highly variable within and among study sites, but four of six sites matched our predictions. A tagging study confirmed these results and demonstrated a substantial proportion of individuals moved away from perennial reaches and into newly wetted intermittent reaches. However, site and species‐specific relationships were variable and likely depended on the habitat, metacommunity dynamics, and life history strategies. Findings suggest that species dispersal dynamics, in addition to recruitment and mortality, should be carefully considered when interpreting species responses to varying water levels, particularly in intermittent stream networks where access to habitat can change drastically with water availability.

Abundance-based dissimilarity measurements reveal higher heterogeneity of fish communities in the lotic habitats of the Yangtze-Caizi transitional floodplain

Abstract Driven by seasonal flood pulses, fish species inhabiting floodplains migrate between lotic and lentic habitat patches to complete their life histories, which can result in the severely species turnover or nestedness. However, these spatiotemporal dynamics of fish metacommunities (beta diversity) were barely quantified. Previous studies either based on species incidence data in calculating beta diversity or solely focus on partial habitat (lotic or lentic) were widely criticized for their misleading results. Here, we addressed the issue by comparing the taxonomic and functional differences in beta diversity and the turnover and nestedness components between wet and dry seasons in the Yangtze-Caizi transitional floodplain. The calculating of beta diversity based on both incidence and abundance data were also compared respectively to test their sensitivity in revealing fish metacommunity dynamics triggered by flood pulses. Regionally in the studied transitional floodplain, we detected significantly taxonomic and functional homogenization of fish assemblages triggered by floods in the high-water period. Then locally within the lotic habitats, our results demonstrated significantly higher overall beta diversity and the turnover components in both the high and low waters. Meanwhile, the significantly higher Local Contributions to Beta Diversity (LCBD) also indicated the higher uniqueness of lotic habitats. These findings highlighted remarkably heterogeneous fish assemblages in lotic habitats, thus deserving higher conservation priority in contrast with lentic habitats. Comparing with classic incidence-based measurements, our results exhibited higher sensitivity of abundance-based approaches in revealing homogeneous or heterogeneous patterns of fish metacommunities influenced by floods. Our results highlighted the importance of employing abundance-based data to measure beta diversity within small spatial extents.

Trophic‐specific responses to migration in empirical metacommunities

The metacommunity, as it evolved from Levins's metapopulation, provides a framework to consider the spatial organization of species interactions. A defining feature of metapopulations and metacommunities is that organisms (populations or communities) are connected via migration. An important result from Levins's metapopulation work – that increasing migration lowers regional extinction probability – is often incorporated into conceptions of metacommunities; however, this may not hold true for multiple interacting metapopulations (i.e. metacommunities). We report results from a metacommunity field experiment conducted with a tropical terrestrial leaf litter macro‐arthropod community. We show that migration induces regional extinctions of predators without significantly changing the predator community composition. For non‐predators we found no evidence of regional extinctions, but a significant change in community composition. Our result corroborates the findings of a prior similar metacommunity experiment with a temperate forest leaf litter community. The concordance between these experiments, even with vastly different communities, highlights the importance of considering trophic and non‐trophic community structure to understand metacommunity dynamics, and suggests a potential connection between migration rates and trophic‐specific responses in ecological communities.

Dynamics of ground-dwelling arthropod metacommunities in intermittent streams: The key role of dry riverbeds

Intermittent streams are subject to high levels of environmental variation. However, little is known about how biota responds to river drying across the channel-to-upland habitat gradient. This is an important shortcoming because assumes that intermittent river habitats and metacommunities are static. Here we studied how river drying affects the spatial and temporal variation in ground-dwelling arthropod communities (spiders, beetles, and ants) across the lateral habitat gradient. We asked whether particular habitats, moments, or species contribute disproportionally to beta diversity. To this end, we monitored two perennial-intermittent reach pairs during an entire drying cycle, and applied beta-diversity partitioning methods to highly-resolved taxonomy data. We predicted that: (i) intermittent reaches would accumulate higher levels of diversity (alpha and beta) than perennial reaches; (ii) dry riverbeds would harbor more species and more unique species; (iii) alpha and beta diversity would be temporally more variable in intermittent than in permanent reaches; and (iv) species dispersal limitation would explain variation in contributions to beta diversity. Intermittent reaches presented higher alpha and beta diversity, with dry channels harboring more unique species and more species than any other habitat. Arthropod metacommunities were more variable across space than over time, and temporal turnover was significant—with species dispersal limitation being positively associated with contributions to beta diversity. Our results elevate the role of dry channels in intermittent river ecology, and show that previous research has likely underestimated their contributions to river-wide biodiversity. Our findings call for the need to integrate the dry phase of intermittent streams into monitoring and conservation programs.

Fragmentation reduces the importance of niche‐based factors relative to dispersal traits in structuring temperate forest understories

AbstractAimThe relative importance of stochastic and deterministic niche processes can affect the assembly of communities in response to land use context and change. In this study, we quantified the relative importance of dispersal‐ vs niche‐based processes in structuring forest plant metacommunities and sought to understand how these processes have changed in these forests over the past 50 years.LocationWisconsin, USA.MethodsWe used plant understorey community survey data in both the 1950s and 2000s from 142 upland forest stands in southern and northern Wisconsin forests to relate compositional similarity to geographic and environmental distances among sites (reflecting dispersal and niche‐based processes, respectively). We then partitioned the variance to determine their relative importance over time. Finally, we classified species into three dispersal groups based on seed mass, dispersal mode, and plant height to assess how these affect community structure.ResultsBoth niche and dispersal processes influence the structure of Wisconsin's forest plant understories. Niche‐based processes related to environmental differences among sites dominate the mostly continuous northern upland forests. In contrast, dispersal processes dominate community assembly in the more fragmented southern upland forests. Dispersal processes increased in importance in both regions and especially in more fragmented southern upland forests over the past 50 years. We detected no differences among dispersal groups in how similarity decays with geographic distance.ConclusionsIn regions retaining heavy forest cover, niche‐based assembly still predominates while in areas with smaller scattered patches of forest, stochastic dispersal plays a greater role. Dispersal‐based processes increasingly dominate forest metacommunity dynamics in both regions.

Spatial disturbance synchrony alters the association of food chain length and ecosystem size

AbstractThe origin of variation in food chain length (FCL) has long been a central topic of ecology due to its influences on trophic control, energy flow and bioaccumulation of environmental contaminants. The positive association of FCL and ecosystem size has been consistently supported in natural systems. Recent studies, however, have begun to report no effects of ecosystem size on FCL. The emerging inconsistency among previous studies implies the existence of overlooked factors that can modulate the relationship between FCL and ecosystem size. Here, we developed a mathematical model describing metacommunity dynamics to show that large ecosystems do not necessarily support long food chains in the presence of spatially correlated disturbance. Our simple model predicted that the effect of ecosystem size was strongly dependent on the spatial extent of disturbance synchrony. When the spatial correlation of disturbance was weak, the positive association between FCL and ecosystem size appeared. However, the relationship of FCL and ecosystem size became more complex, including hump‐shaped and multimodal forms, as the spatial extent of disturbance synchrony increases. This pattern emerged because larger ecosystems have wider aerial coverage, so more chances exist that an episodic disturbance hits some of the habitat patches and spreads across the landscape. Our finding highlights the important role of spatial disturbance synchrony in driving FCL, providing insights into why ecosystem size effects are variable across systems.

What can observational data reveal about metacommunity processes?

A key challenge for community ecology is to understand to what extent observational data can be used to infer the underlying community assembly processes. As different processes can lead to similar or even identical patterns, statistical analyses of non‐manipulative observational data never yield undisputable causal inference on the underlying processes. Still, most empirical studies in community ecology are based on observational data, and hence understanding under which circumstances such data can shed light on assembly processes is a central concern for community ecologists. We simulated a spatial agent‐based model that generates variation in metacommunity dynamics across multiple axes, including the four classic metacommunity paradigms as special cases. We further simulated a virtual ecologist who analysed snapshot data sampled from the simulations using eighteen output metrics derived from beta‐diversity and habitat variation indices, variation partitioning and joint species distribution modelling. Our results indicated two main axes of variation in the output metrics. The first axis of variation described whether the landscape has patchy or continuous variation, and thus was essentially independent of the properties of the species community. The second axis of variation related to the level of predictability of the metacommunity. The most predictable communities were niche‐based metacommunities inhabiting static landscapes with marked environmental heterogeneity, such as metacommunities following the species sorting paradigm or the mass effects paradigm. The most unpredictable communities were neutral‐based metacommunities inhabiting dynamics landscapes with little spatial heterogeneity, such as metacommunities following the neutral or patch sorting paradigms. The output metrics from joint species distribution modelling yielded generally the highest resolution to disentangle among the simulated scenarios. Yet, the different types of statistical approaches utilized in this study carried complementary information, and thus our results suggest that the most comprehensive evaluation of metacommunity structure can be obtained by combining them.

On the importance of temporal meta-community dynamics for our understanding of assembly processes

A recommendation of: Franck Jabot, Fabien Laroche, Francois Massol, Florent Arthaud, Julie Crabot, Maxime Dubart, Simon Blanchet, Francois Munoz, Patrice David, Thibault Datry Assessing metacommunity processes through signatures in spatiotemporal turnover of community composition 10.1101/480335

Cross-scale dynamics in community and disease ecology: relative timescales shape the community ecology of pathogens.

Communities of free-living organisms are shaped by processes operating within and among patches of habitat, whereas pathogen communities are shaped by analogous processes operating within and among hosts. Resource competition (R*) theory can describe dynamics within patches or hosts, and metacommunity dynamics describe competition-colonization trade-offs, extinction debts, and superinfection. However, models at this broader scale often assume instantaneous competitive exclusion in co-inhabited patches or co-infected hosts. Impacts of more gradual competitive exclusion on the abundance, distribution, and diversity of species are less clear. Here, we nest a general resource competition model within a metacommunity framework and manipulate the relative timescales for processes operating within and among patches/hosts. We focus on superinfection in pathogen communities. We compare cases where transmission depends on infection prevalence vs. the abundance of pathogens within hosts. Surprisingly, slowing the relative pace of competitive exclusion within hosts can decrease infection prevalence of the inferior competitor and increase prevalence of the superior competitor, depending on transmission and virulence. Slower within-host dynamics reduce the abundance of both pathogens within hosts and promote diversity at multiple scales: co-infections within individual hosts and co-occurrence in the host population. These results highlight surprising feedbacks that can emerge across scales and reinforce the rich cross-scale connections between community and disease ecology.

Fifteen important questions in the spatial ecology of diatoms

Abstract Recently, studies about the spatial distribution of microbial species and communities have increased substantially. Freshwater diatoms are used as one of the most popular model taxa in such macroecological studies, but the most exciting patterns in the spatial ecology of diatoms have not been reviewed. Here, we identify 15 important questions about freshwater diatom ecology, review the major findings, and suggest novel research avenues. We found that diatoms do not support classical latitudinal diversity gradient, species–area relationship or Rapoport's rule. We found some, albeit inconsistent support for an elevational diversity gradient, Bergmann's rule and niche conservation. Diatoms do support a positive interspecific abundance–occupancy relationship like nearly all other taxa. With regards to metacommunity dynamics, diatom communities are typically structured by species sorting, but neutral dynamics or mass effects are also evident at large or small spatial scale, respectively. Taken together, this review suggests that diatoms follow some classical biogeographical patterns similarly to larger taxa, but patterns are typically weaker than for macro‐organisms. This may result because diatoms are typically relatively strongly controlled by local factors and often exhibit efficient stochastic dispersal processes both at small and large scales. More research is needed to build a more comprehensive view of diatom species–area relationships and latitudinal gradients in diversity, for example. In the future, well‐replicated macroecological field experiments, diatom studies with intercontinental or global coverage, trait‐based approaches, and DNA‐based species identification would be fruitful avenues to shed more light into the spatial ecology of diatoms.

Dynamic contributions of intermittent and perennial streams to fish beta diversity in dryland rivers

AbstractAimTo determine the role of flow intermittence and species origin in shaping freshwater fish beta diversity across dryland riverscapes.LocationVerde and Little Colorado River basins, United States.MethodsFish beta diversity was investigated in two large rivers with marked differences in basin‐wide flow intermittence. Local site (continually flowing perennial vs. periodically flowing intermittent) and species (native vs. non‐native) contributions to beta diversity were compared within each basin and over multiple decades (1987–2013) in relation to changing hydrologic conditions. Metacommunity dynamics were quantified using changes in alpha‐ (local), beta‐ and gamma‐ (regional) diversity through time.ResultsBeta‐diversity patterns varied in relation to basin‐wide intermittence. Intermittent sites were most influential to beta diversity where basin‐wide intermittence was lower (Verde River), whereas perennial sites were most influential where basin‐wide intermittence was higher (Little Colorado River). In intermittent sites, native fish species contributions to beta diversity tended to be higher than non‐native species contributions. The relative contributions of perennial and intermittent sites to β‐diversity within each basin were invariant to annual flow regimes, whether atypically lower or higher than average flows, but somewhat related to intra‐annual flow variation. Native species contributions to β‐diversity increased in years with high flow conditions in the Verde River. Over time, beta diversity decreased in the lower intermittence Verde River, indicating taxonomic homogenization, but remained relatively unchanged in the Little Colorado River.Main ConclusionsInvestigations of beta‐diversity components over time are considered pivotal for conservation prioritization and planning. We found that both intermittent and perennial streams play complementary roles in supporting fish beta diversity, and that their relative contributions increase as basin wide availability of the habitat type decreases. Moreover, contributions of intermittent streams to overall beta diversity were relatively consistent through time and supported native fish diversity. Despite weakening policy protections of intermittent streams, these habitats are critical for supporting local species persistence and regional biodiversity.

Untangling the assembly of macrophyte metacommunities by means of taxonomic, functional and phylogenetic beta diversity patterns

Metacommunity ecology has broadened considerably with the recognition that measuring beta diversity beyond the purely taxonomic viewpoint may improve our understanding of the dispersal- and niche-based mechanisms across biological communities. In that perspective, we applied a novel multidimensional approach including taxonomic, functional and phylogenetic data to enhance our basic understanding of macrophyte metacommunity dynamics. For each beta diversity metric, we calculated the mean overall value and tested whether the mean value was different from that expected by chance using null models. We also employed evolutionary and spatially constrained models to first identify the degree to which the studied functional traits showed a phylogenetic signal, and then to estimate the relative importance of spatial and environmental effects on metacommunity structure. We first found that most individual ponds were inhabited by species that were merely random draws from the taxonomic and phylogenetic species pool available in the study region. Contrary to our expectations, not all measured traits were conserved along the phylogeny. We also showed that trait and phylogenetic dimensions strongly increased the amount of variation in beta diversity that can be explained by degree of environmental filtering and dispersal limitation. This suggests that accounting for functional traits and phylogeny in metacommunity ecology helps to explain idiosyncratic patterns of variation in macrophyte species distribution. Importantly, phylogenetic and functional analyses identified the influence of underlying mechanisms that would otherwise be missed in an analysis of taxonomic turnover. Together, these results let us conclude that macrophyte species have labile functional traits adapted to dispersal-based processes and some evolutionary trade-offs that drive community assembly via species sorting. Overall, our exploration of different facets of beta diversity showed how functional and phylogenetic information may be used with species-level data to test community assembly hypotheses that are more ecologically meaningful than assessments of environmental patterns based on the purely taxonomic viewpoint.

Zoochory of zooplankton: seasonality and bird morphological diversity can influence metacommunity dynamics of temporary ponds

Abstract Harsh and unstable aquatic environments present selective forces that influence environmental heterogeneity, dispersal capacity and specific life history strategies that, in turn, affect species distribution and metacommunity dynamics. To date, relatively few studies have examined the potential of bird-mediated dispersal to connect isolated ephemeral habitats. We used zooplankton from temporary ponds to examine the effects of bird morphological diversity and water availability on microcrustacean diversity in temporary ponds. Three bird feet models were constructed based on small, large and webbed anisodactylous forms in order to simulate bird walking on the pond shore. Bird and zooplankton communities were sampled in two temporary ponds and experimentally simulated zooplankton dispersal by bird on dry sediments. We surveyed in two contrasting seasonal periods. Overall, water availability does affect zooplankton composition, and birds with large feet have higher dispersal capacity. In addition, birds with different feet size and shape carry distinct zooplankton species. During the dry season, sediments hold 100% more species than in the wet season, which indicates that birds have higher potential for dispersing zooplankton in drought conditions. Our findings suggest that bird diversity can maintain zooplankton metacommunities by rescuing dormant organisms from dry ponds and connecting to any available aquatic habitats.

Darwin's finches: a model of landscape effects on metacommunity dynamics in the Galápagos Archipelago

Darwin's finches represent a dynamic radiation of birds within the Galápagos Archipelago. Unlike classic island radiations dominated by island endemics and intuitive ‘conveyer belt’ colonization with little subsequent dispersal, species of Darwin's finches have populations distributed across many islands and each island contains complex metacommunities of closely related birds. Understanding the role of metacommunity and structured population dynamics in speciation within this heterogeneous island system would provide insights into the roles of fragmentation and dispersal in evolution. In this study, a large multi‐species dataset and a comparative ground finch dataset (two co‐distributed lineages) were used to show how landscape features influence patterns of gene flow across the archipelago. Factors expected to regulate migration including distance and movement from large, central islands to small, peripheral islands were rejected in the multi‐species dataset. Instead, the harsh northeast islands contributed individuals to the larger central islands. Successful immigration relies on three factors: arriving, surviving and reproducing, thus the dispersal towards the central islands may be either be due to more migrants orienting towards these land masses due to their large size and high elevation, or may reflect a higher likelihood of survival and successful reproduction due to the larger diversity of habitats and more environmentally stable ecosystems that these islands possess. Further, the overall directionality of migration was south‐southwest against the dominant winds and currents. In comparing dispersal between the common cactus finch and medium ground finch, both species had similar migration rates but the cactus finch had approximately half the numbers of migrants due to lower effective populations sizes. Significant population structure in the cactus finch indicates potential for further speciation, while the medium ground finch maintains cohesive gene flow across islands. These patterns shed light on the macroevolutionary patterns that drive diversification and speciation within a radiation of highly‐volant taxa.

Dormancy in Metacommunities.

Although metacommunity ecology has improved our understanding of how dispersal affects community structure and dynamics across spatial scales, it has yet to adequately account for dormancy. Dormancy is a reversible state of reduced metabolic activity that enables temporal dispersal within the metacommunity. Dormancy is also a metacommunity-level process because it can covary with spatial dispersal and affect diversity across spatial scales. We develop a framework to integrate dispersal and dormancy, focusing on the covariation they exhibit, to predict how dormancy modifies the importance of species interactions, dispersal, and historical contingencies in metacommunities. We used empirical and modeling approaches to demonstrate the utility of this framework. We examined case studies of microcrustaceans in ephemeral ponds, where dormancy underlies metacommunity dynamics, and identified constraints on the dispersal and dormancy strategies of bromeliad-dwelling invertebrates. Using simulations, we showed that dormancy can alter classic metacommunity patterns of diversity in ways that depend on dispersal-dormancy covariation and spatiotemporal environmental variability. We propose that dormancy may also facilitate evolution-mediated priority effects if locally adapted seed banks prevent colonization by more dispersal-limited species. Last, we present testable predictions for the implications of dormancy in metacommunities, some of which may fundamentally alter our understanding of metacommunity ecology.

Spatiotemporal distribution of seasonal bird assemblages on land-bridge islands: linking dynamic and static views of metacommunities

BackgroundAlthough assessing temporal dynamics of populations is crucial for understanding metacommunities, empirical studies have primarily analyzed only static snapshots of communities. Here, we present a holistic view of how species traits and habitat characteristics relate to metacommunity dynamics and use it to test for differences in the spatiotemporal distribution of seasonal bird assemblages.MethodsWe surveyed forest birds in breeding and winter seasons within 36 islands for 9 years. We then grouped birds into four landbird assemblages, selected on the basis of published differences in biology or ecology: winter residents, migratory winter visitors, breeding summer residents, and migratory summer visitors. We estimated dynamic species colonization and extirpation through the 9-year period, and evaluated the associations among island attributes, species attributes and community composition.ResultsOverall, winter and summer residents showed strong associations between composition and habitat structure of the islands. In addition, winter and summer residents on large islands had lower extirpation and turnover than winter and summer visitors. Visitor assemblages showed no significant habitat associations, and in winter had high extirpation rates and small body sizes. By contrast, local extirpation of summer visitors was correlated with local species richness, indicating a likely effect of competition on extirpation.ConclusionsOur results demonstrated repeated patterns among species composition, bird traits, habitat/island characteristics and observed metacommunity dynamics. Winter and summer residents best matched species sorting and patch dynamics, respectively, due to differences in resource availability and requirements of overwinter survival versus breeding. Summer visitors were consistent with species sorting and winter visitors were randomly distributed, likely because of interactions with resident competitors. Our results highlight that coexisting seasonal migrant and resident assemblages differ in their spatial dynamics, with consequences for relevant conservation and management strategies.