Studies Of Community Assembly Research Articles

Extending trait dispersion across trophic levels: Predator assemblages act as top-down filters on prey communities.

Studies of community assembly typically focus on the effects of abiotic environmental filters and stabilizing competition on functional trait dispersion within single trophic levels. Predation is a well-known driver of community diversity and composition, yet the role of functionally diverse predator communities in filtering prey community traits has received less attention. We examined functionally diverse communities of predators (fishes) and prey (epifaunal crustaceans) in eelgrass (Zostera marina) beds in two northern California estuaries to evaluate the filtering effects of predator traits on community assembly and how filters acting on predators influence their ability to mediate prey community assembly. Fish traits related to bottom orientation were correlated with more clustered epifauna communities, and epifauna were generally overdispersed while fishes were clustered, suggesting prey may be pushed to disparate areas of trait space to avoid capture by benthic sit-and-wait predators. We also found correlations between the trait dispersions of predator and prey communities that strengthened after accounting for the effects of habitat filters on predator dispersion, suggesting that habitat filtering effects on predator species pools may hinder their ability to affect prey community assembly. Our results present compelling observational evidence that specific predator traits have measurable impacts on the community assembly of prey, inviting experimental tests of predator trait means on community assembly and explicit comparisons of how the relative effects of habitat filters and intraguild competition on predators impact their ability to affect prey community assembly. Integrating our understanding of traits at multiple trophic levels can help us better predict the impacts of community composition on food web dynamics as regional species pools shift with climate change and anthropogenic introductions.

Complete genome sequences of six duckweed-associated bacterial strains for studying community assembly in synthetic plant microbiome.

We report the complete genome sequences of six bacterial strains isolated from a floating macrophyte, duckweed. These six strains, representing the six dominant families of the natural duckweed microbiome, establish a simple model ecosystem when inoculated onto sterilized duckweed. Their genomes would provide insights into community assembly in plant microbiome.

Biotic and abiotic factors drive multi-trophic interactions among spiders at different spatial scales in urban greenspaces

Abstract Urbanization is often detrimental to biodiversity, yet urban greenspaces can be managed to provide habitat for many arthropods. Understanding how anthropogenic filters influence processes of community assembly in urban ecosystems will inform conservation of species such as spiders, which provide natural pest control. Spiders are abundant in urban areas, but the relative importance of biotic and abiotic factors for structuring spider communities in urban greenspaces is unclear. We initiated the Cleveland Pocket Prairie Project in the legacy city of Cleveland, Ohio, where vacant lots and urban prairies were established across eight inner-city neighborhoods. In each greenspace, spiders were collected along with landscape and local environmental data in July 2017. Using a path analysis approach, we investigated the relative importance and strength of landscape and local environmental filters for influencing the structure of spider communities during mid-summer within this system. We found that spider community assembly was influenced by multiple abiotic and biotic drivers across spatial scales related to landscape composition, soil texture and quality, prey breadth, and habitat management designs. Web-building and active hunting spiders responded differently to these landscape and local drivers, highlighting the need to incorporate a functional perspective when studying community assembly. These findings suggest that a multi-scale approach to conservation management is needed to support biodiversity and associated biological control services in urban ecosystems.

Inverse priority effects: A role for historical contingency during species losses.

Communities worldwide are losing multiple species at an unprecedented rate, but how communities reassemble after these losses is often an open question. It is well established that the order and timing of species arrival during community assembly shapes forthcoming community composition and function. Yet, whether the order and timing of species losses can lead to divergent community trajectories remains largely unexplored. Here, we propose a novel framework that sets testable hypotheses on the effects of the order and timing of species losses-inverse priority effects-and suggests its integration into the study of community assembly. We propose that the order and timing of species losses within a community can generate alternative reassembly trajectories, and suggest mechanisms that may underlie these inverse priority effects. To formalize these concepts quantitatively, we used a three-species Lotka-Volterra competition model, enabling to investigate conditions in which the order of species losses can lead to divergent reassembly trajectories. The inverse priority effects framework proposed here promotes the systematic study of the dynamics of species losses from ecological communities, ultimately aimed to better understand community reassembly and guide management decisions in light of rapid global change.

Community assembly of the human piercing microbiome.

Predicting how biological communities respond to disturbance requires understanding the forces that govern their assembly. We propose using human skin piercings as a model system for studying community assembly after rapid environmental change. Local skin sterilization provides a 'clean slate' within the novel ecological niche created by the piercing. Stochastic assembly processes can dominate skin microbiomes due to the influence of environmental exposure on local dispersal, but deterministic processes might play a greater role within occluded skin piercings if piercing habitats impose strong selection pressures on colonizing species. Here we explore the human ear-piercing microbiome and demonstrate that community assembly is predominantly stochastic but becomes significantly more deterministic with time, producing increasingly diverse and ecologically complex communities. We also observed changes in two dominant and medically relevant antagonists (Cutibacterium acnes and Staphylococcus epidermidis), consistent with competitive exclusion induced by a transition from sebaceous to moist environments. By exploiting this common yet uniquely human practice, we show that skin piercings are not just culturally significant but also represent ecosystem engineering on the human body. The novel habitats and communities that skin piercings produce may provide general insights into biological responses to environmental disturbances with implications for both ecosystem and human health.

Decoupled functional and phylogenetic diversity provide complementary information about community assembly mechanisms: A case study of Greek forests

Understanding the mechanisms of community assembly is of great importance to biogeography and ecology. Simultaneous investigation of the functional and phylogenetic facets of diversity has been proposed as a useful approach that allows inferences about such mechanisms. This study applies such an approach to explore diversity and structure within and among the main plant community types of mountainous forests in northern and central Greece. Functional and phylogenetic diversity and structure were measured in 25 community types of broadleaved deciduous and mountainous coniferous forests. Functional richness and Faith’s phylogenetic diversity were used to assess diversity, while mean pairwise functional and phylogenetic distances were used to investigate structure. Relationships between both facets of diversity and structure, as well as community types, were tested using boosted regression trees separately for all vascular plant taxa and taxa occurring in the forest understorey. Phylogenetic diversity was positively correlated with functional diversity, but phylogenetic structure was not a good predictor of functional structure. The understorey dataset revealed non-random structure for more vegetation plots than the dataset with all taxa. Habitat effects, represented by community types, were found to be better predictors of functional structure than phylogenetic structure, highlighting the need to account for habitat variability in studies of community assembly. In our study system, the two diversity facets provide complementary information on the structure of community types since most of the vegetation plots studied were found statistically significantly structured for one diversity facet (functionally clustered or phylogenetically overdispersed) and random for the other. Our results indicate that functional and phylogenetic measures provide different insights into the mechanisms driving the assembly of the forest community types studied.

Bird traits and their nutrient impact on terrestrial invertebrate populations

AbstractBirds are a large nutrient vector from marine to terrestrial environments where the increased nutrient input typically results in greater primary production and enhanced microbial activity. Associated invertebrate populations however, show large response variability to bird nutrient subsidies. To explain this variable invertebrate response, we performed a meta-analysis (50 articles ranging from polar to tropical regions) where we compared the effect of bird presence on invertebrate populations between: bird taxa, nesting site selection, bird diet and climate regions. In addition, we quantified how different invertebrate taxa and trophic guilds respond to the presence of birds. Invertebrate abundance was on average > 1000% higher by bird presence, but there was little evidence for any specific bird-taxa effects on invertebrate abundance responses. Birds with a mixed diet increased Coleoptera populations the most. Invertebrate responses to bird presence were largest in polar regions but variation remained high. Not all species within communities responded to bird presence, indicating that nutrient limitation is species-specific or ecosystems are affected in different ways by birds. Furthermore, sampling strategies were inconsistent and may impact effect-sizes. Despite the contrasting nature of the different studies, an overall positive invertebrate abundance response was found in the presence of birds, with larger responses observed in polar regions. Standardized sampling approaches would resolve much of the remaining variability. As natural experiments, bird nests and affected areas are a prime spot to study community assembly rules and address issues of anthropogenic disturbance and climate change.

Drivers of Insect Community Change along the Margins of Mountain Streams in Serra da Estrela Natural Park (Portugal)

Mountain ecosystems are important biodiversity hotspots and valuable natural laboratories to study community assembly processes. Here, we analyze the diversity patterns of butterflies and odonates in a mountainous area of high conservation value-Serra da Estrela Natural Park (Portugal)-and we assess the drivers of community change for each of the two insect groups. The butterflies and odonates were sampled along 150 m transects near the margins of three mountain streams, at three elevation levels (500, 1000, and 1500 m). We found no significant differences in odonate species richness between elevations, but marginal differences (p = 0.058) were found for butterflies due to the lower number of species at high altitudes. Both insect groups showed significant differences in beta diversity (βtotal) between elevations, with species richness differences being the most important component for odonates (βrich = 55.2%), while species replacement drove the changes between butterfly assemblages (βrepl = 60.3%). Climatic factors, particularly those depicting harsher conditions of temperature and precipitation, were the best predictors of total beta diversity (βtotal) and its components (βrich, βrepl) for the two study groups. The study of insect biodiversity patterns in mountain ecosystems and of the role played by different predictors contribute to further our understanding on the community assembly processes and may help to better predict environmental change impacts on mountain biodiversity.

Increasing land-use durations enhance soil microbial deterministic processes and network complexity and stability in an ecotone

Studies of community assembly and species interactions are updating our view of the mechanisms underpinning microbial diversity in single-type ecosystems, yet they are rarely conducted in ecotones, such as the agro-pastoral ecotone of northern China (APEN) undergoing frequent land-use conversions. In this study, soil microbial assembly processes and co-occurrence patterns were examined in different land-use types and durations across the APEN. The interpretation of remote sensing images revealed that current land-use types lasted 1 to 9 years for all samples. None of measured soil properties changed significantly between cropland and grassland, while silt and sand differed between the long (5 to 9 years) and short (1 to 4 years) duration. Soil microbial communities were assembled under consistent processes in both land-use types, but determinism clearly exhibited greater influences in the long duration than in the short one. The β-nearest taxon index (βNTI) decreased significantly with the durations in all samples and was also affected by total nitrogen (TN), soil organic matter (SOM), total phosphorus (TP), and clay. For the co-occurrence networks, nodes, edges, modularity, and the proportion of negative edges were similar between cropland and grassland, but obviously higher in the long duration than in the short one. Simultaneously, these metrics of the sub-networks had strong positive correlations with the durations, and weaker but significant correlations with TN, SOM, silt, and sand. Altogether, this study demonstrated that frequent land-use conversions might alleviate the impact of current land-use types, but highlight the importance of land-use durations on soil microbial community assembly and co-occurrence patterns in the APEN, and the deterministic processes and network complexity and stability increased with the durations, which advance the understanding of the mechanisms maintaining soil microbial diversity in ecotones.

Evidence for the intermediate disturbance hypothesis and exponential decay in replacement in Streptococcus pneumoniae following use of conjugate vaccines

Understanding how pneumococci respond to pneumococcal conjugate vaccines (PCVs) is crucial to predict the impact of upcoming higher-valency vaccines. However, stages in pneumococcal community succession following disturbance are poorly understood as long-time series on carriage are scarce and mostly evaluated at end-point measurements. We used a 20-year cross-sectional dataset of pneumococci carried by Portuguese children, and methods from community ecology, to study community assembly and diversity following use of PCV7 and PCV13. Two successional stages were detected upon introduction of each PCV: one in which non-vaccine serotypes increased in abundance, fitted by a broken-stick model, and a second in which the community returned to the original structure, fitted by a geometric series, but with different serotype profile and a drop in richness as great as 24%. A peak in diversity was observed for levels of intermediate vaccine uptake (30–40%) in agreement with the intermediate disturbance hypothesis. Serotype replacement was fitted by an exponential decay model (R2 = 80%, P < 0.001). The half-life for replacement was 8 years for PCV7 and 10 years for PCV13. The structure of the pneumococcal community is resilient to vaccine pressure. The increasing loss of diversity, however, suggests it could eventually reach a threshold beyond which it may no longer recover.

Zooplankton recovery from a whole‐lake disturbance: Examining roles of abiotic factors, biotic interactions, and traits

AbstractCommunity assembly following disturbance is a key process in determining the composition and function of the future community. However, replicated studies of community assembly at whole‐ecosystem scales are rare. Here, we describe a series of whole‐lake experiments, in which the recovery of zooplankton communities was tracked following an ecosystem‐scale disturbance, that is, application of the piscicide, rotenone. Using a before‐after‐control‐impact design, 14 lakes in eastern Washington were studied: Seven lakes were treated with rotenone, while seven lakes acted as reference systems. Each lake was monitored up to 6 months before and 1–2 years after the rotenone treatments. Zooplankton samples and environmental measurements were collected approximately monthly from each lake. Community responses following disturbance were assessed using metrics of abundance, diversity, and community composition, as well as taxonomic group abundance. Zooplankton recovery was also assessed using species traits related to habitat, feeding mode, trophic level, body size, and life history. In addition to patterns of recovery, potential mechanisms were explored relating to abiotic conditions, biotic interactions, and traits. There were steep declines in the abundance (average across years: 99%) and diversity (average across years: 75%) of the zooplankton community following rotenone treatment. Although abundance had recovered by the second year of the study, community diversity had not fully recovered after 2 years. Communities from rotenone lakes appeared to be compositionally recovered within about 8 months following disturbance. Cyclopoid copepods were typically the first group to recover and remained dominant for a few months, whereas cladocerans recovered more slowly, typically within ~6–7 months following rotenone. Calanoid copepods were not fully recovered 2 years after rotenone treatment. Traits related to body size and feeding mode were associated with the zooplankton communities following rotenone treatment. We failed to observe significant spatial synchrony in recovery patterns of zooplankton across lakes, though we did observe significant synchrony of zooplankton taxonomic groups within lakes. These findings suggest that traits related to ecological function, and to a lesser extent, biotic, and abiotic factors, as well as characteristics of the disturbance itself, may be important in helping to understand recovery processes.

Network-based analysis reveals differences in plant assembly between the native and the invaded ranges

Associated with the introduction of alien species in a new area, interactions with other native species within the recipient community occur, reshaping the original community and resulting in a unique assemblage. Yet, the differences in community assemblage between native and invaded ranges remain unclear. Mediterranean grasslands provide an excellent scenario to study community assembly following transcontinental naturalisation of plant species. Here, we compared the community resemblance of plant communities in Mediterranean grasslands from both the native (Spain) and invaded (Chile) ranges. We used a novel approach, based on network analysis applied to co-occurrence analysis in plant communities, allowing us to study the co-existence of native and alien species in central Chile. This useful methodology is presented as a step forward in invasion ecology studies and conservation strategies. We found that community structure differed between the native and the invaded range, with alien species displaying a higher number of connections and, therefore, acting as keystones to sustain the structure within the invaded community. Alien species acting like keystones within the Chilean grassland communities might exacerbate the threat posed by biological invasions for the native biodiversity assets. Controlling the spread of the alien species identified here as keystones should help managing potential invasion in surrounding areas. Network analyses is a free, easy-to-implement and straightforward visual tool that can be widely used to reveal shifts in native communities and elucidate the role of multiple invaders into communities.

Environmental Heterogeneity Affecting Community Assembly Patterns and Phylogenetic Diversity of Three Forest Communities at Mt. Huangshan, China

Studying community assembly has always been a central issue in ecological research and is necessary for understanding mechanisms of species coexistence and biodiversity. Environmental heterogeneity is a driver of biodiversity, but much remains to be learned about how evolutionary processes are affected by environmental factors. We aimed to clarify the evolutionary processes in different vegetation communities in the Huangshan Scenic Area, Anhui Province, China. We constructed a phylogenetic tree of these communities based on a constraint tree and three DNA barcode regions. Community I was characterized by a weakly overdispersed phylogenetic structure for all three plant groups. The structure of Community II showed clustered for total plants and shrubs, overdispersed for trees. However, the phylogenetic structure was clustered for total plants, overdispersed for trees and shrubs in Community III. The main drivers of these patterns were spatial and climatic factors. Phylogenetic α-diversity had a significant positive relationship with species richness. The values of phylogenetic β-diversity reached their maximum at intermediate elevations among three vegetation communities for total plants. The main factors that affected diversity patterns were spatial variables, not climatic factors, indicating that environmental heterogeneity determined the mechanisms of biodiversity and species coexistence in the community. Our results showed that deterministic processes may control community assembly in three different vegetation regions.

How to measure flower ultraviolet reflectance using digital photography

AbstractAimsFlower ultraviolet (UV) reflectance strongly influences insects’ ability to detect flowers and locate pollen/nectar sources. Although included in the TRY database, the lack of a cost‐effective standardised method of measurement hampers the availability of information on this key floral trait. Digital photography and image processing allow for a novel approach to flower UV reflectance measurement that is both accessible and accurate.LocationEuropean semi‐natural grasslands.MethodsWe used a UV‐LED light and a mirrorless camera with a filter, which represents a low‐cost equipment for narrow emission/reflection photography (350–380 nm). Flowers were photographed with two standards of known reflection, and UV reflectance values were obtained using open‐source image processing software. We measured UV reflectance for 57 plant species typical of European semi‐natural grasslands.ResultsOur values substantially matched the categorical classes obtained by analogue photography available in TRY and showed a highly significant relationship with spectrophotometric measures.ConclusionsThe method proposed here overcomes the one based on analogue photography and subjective visual estimates, and represents an easy and low‐cost alternative to spectrophotometry. It may promote the standardised measurement of flower UV reflectance and broaden the information of this trait globally, meeting the needs of functional ecology and trait‐based community assembly studies.

Spatiotemporal interactions of a novel mesocarnivore community in an urban environment before and during SARS-CoV-2 lockdown.

Studying species interactions and niche segregation under human pressure provides important insights into species adaptation, community functioning and ecosystem stability. Due to their high plasticity in behaviour and diet, urban mesocarnivores are ideal species for studying community assembly in novel communities.We analysed the spatial and temporal species interactions of an urban mesocarnivore community composed of the red fox Vulpes vulpes and the marten Martes sp. as native species, the raccoon Procyon lotor as invasive species, and the cat Felis catus as a domestic species in combination with human disturbance modulated by the SARS‐CoV‐2 lockdown effect that happened while the study was conducted.We analysed camera trap data and applied a joint species distribution model to understand not only the environmental variables influencing the detection of mesocarnivores and their use intensity of environmental features but also the species’ co‐occurrences while accounting for environmental variables. We then assessed whether they displayed temporal niche partitioning based on activity analyses, and finally analysed at a smaller temporal scale the time of delay after the detection of another focal species.We found that species were more often detected and displayed a higher use intensity in gardens during the SARS‐CoV‐2 lockdown period, while showing a shorter temporal delay during the same period, meaning a high human‐induced spatiotemporal overlap. All three wild species spatially co‐occurred within the urban area, with a positive response of raccoons to cats in detection and use intensity, whereas foxes showed a negative trend towards cats. When assessing the temporal partitioning, we found that all wild species showed overlapping nocturnal activities. All species displayed temporal segregation based on temporal delay. According to the temporal delay analyses, cats were the species avoided the most by all wild species. To conclude, we found that although the wild species were positively associated in space, the avoidance occurred at a smaller temporal scale, and human pressure in addition led to high spatiotemporal overlap.Our study sheds light to the complex patterns underlying the interactions in a mesocarnivore community both spatially and temporally, and the exacerbated effect of human pressure on community dynamics.

Phenotypic plasticity may mediate habitat filtering in a forest edge community

A key process determining community assembly is habitat filtering, which reduces the range of trait values and thus leads to trait convergence. Habitat filtering is often assumed to involve a reduction in species richness, but such trait convergence could also result from phenotypic plasticity. By allowing more species in the community to show the ‘right' phenotype and pass the filter, phenotypic plasticity could maintain species richness despite trait convergence. If phenotypic plasticity plays this role, environmental changes should modify trait distribution but not species composition or richness. We tested this hypothesis in a forest edge community recently invaded by the alien shrub Rubus praecox. We measured functional traits beneath Rubus canopy (Rubus‐invaded community) and in adjacent microsites naturally free from Rubus (original community), comparing trait dispersion and community structure parameters. We also characterized the microenvironments to seek functional explanations for the observed phenotypic changes. The functional dispersion parameter FDis showed habitat filtering in the Rubus‐invaded community (trait convergence), while in the original community it did not differ from a null model. Species richness and composition did not differ between the two communities. Soil characteristics were similar in both communities but light availability was greatly reduced in the Rubus‐invaded community. A principal component analysis of community‐weighted means of functional traits showed that phenotypic changes between communities were mostly consistent with functional responses to shading, including an increase in specific leaf area and a reduction in flavonoid concentration in the Rubus‐invaded community. We verified the conditions necessary to infer that phenotypic plasticity mediates the outcome of habitat filtering driven by Rubus in the study system, i.e. plasticity would explain species persistence despite trait convergence. Phenotypic plasticity, often subsumed within intraspecific variation in community assembly studies, should be considered individually to improve our understanding of the causes and consequences of habitat filtering.

Incorporating human behaviors into theories of urban community assembly and species coexistence

In cities, humans directly and indirectly affect plant and wildlife communities. These human–species interactions are not included in traditional ecological approaches used to understand why and how organisms are distributed. Here, we incorporate human behaviors into urban community assembly theories and detail all the complex ways humans affect the dispersal, selection and persistence of species in cities. To do this, we integrate human behaviors and actions into traditional filter frameworks used to study community assembly. We use our framework to develop testable hypotheses to predict patterns of urban diversity as well as pose key considerations for future research. In order to have a predictive understanding of how urban biodiversity responds to environmental, social and land use change, it is necessary to better understand interactions between humans and other organisms.

Hawai‘i forest review: Synthesizing the ecology, evolution, and conservation of a model system

As the most remote archipelago in the world, the Hawaiian Islands are home to a highly endemic and disharmonic biota that has fascinated biologists for centuries. Forests are the dominant terrestrial biome in Hawai‘i, spanning complex, heterogeneous climates across substrates that vary tremendously in age, soil structure, and nutrient availability. Species richness is low in Hawaiian forests compared to other tropical forests, as a consequence of dispersal limitation from continents and adaptive radiations in only some lineages, and forests are dominated by the widespread Metrosideros species complex. Low species richness provides a relatively tractable model system for studies of community assembly, local adaptation, and species interactions. Moreover, Hawaiian forests provide insights into predicted patterns of evolution on islands, revealing that while some evidence supports “island syndromes,” there are exceptions to them all. For example, Hawaiian plants are not as a whole less defended against herbivores, less dispersible, more conservative in resource use, or more slow-growing than their continental relatives. Clearly, more work is needed to understand the drivers, sources, and constraints on phenotypic variation among Hawaiian species, including both widespread and rare species, and to understand the role of this variation for ecological and evolutionary processes, which will further contribute to conservation of this unique biota. Today, Hawaiian forests are among the most threatened globally. Resource management failures – the proliferation of non-native species in particular – have led to devastating declines in native taxa and resulted in dominance by novel species assemblages. Conservation and restoration of Hawaiian forests now rely on managing threats including climate change, ongoing species introductions, novel pathogens, lost mutualists, and altered ecosystem dynamics through the use of diverse tools and strategies grounded in basic ecological, evolutionary, and biocultural principles. The future of Hawaiian forests thus depends on the synthesis of ecological and evolutionary research, which will continue to inform future conservation and restoration practices.

Relationships between climate and phylogenetic community structure of fossil pollen assemblages are not constant during the last deglaciation.

Disentangling the influence of environmental drivers on community assembly is important to understand how multiple processes influence biodiversity patterns and can inform understanding of ecological responses to climate change. Phylogenetic Community Structure (PCS) is increasingly used in community assembly studies to incorporate evolutionary perspectives and as a proxy for trait (dis)similarity within communities. Studies often assume a stationary relationship between PCS and climate, though few studies have tested this assumption over long time periods with concurrent community data. We estimated two PCS metrics-Nearest Taxon Index (NTI) and Net Relatedness index (NRI)-of fossil pollen assemblages of Angiosperms in eastern North America over the last 21 ka BP at 1 ka intervals. We analyzed spatiotemporal relationships between PCS and seven climate variables, evaluated the potential impact of deglaciation on PCS, and tested for the stability of climate-PCS relationships through time. The broad scale geographic patterns of PCS remained largely stable across time, with overdispersion tending to be most prominent in the central and southern portion of the study area and clustering dominating at the longitudinal extremes. Most importantly, we found that significant relationships between climate variables and PCS (slope) were not constant as climate changed during the last deglaciation and new ice-free regions were colonized. We also found weak, but significant relationships between both PCS metrics (i.e., NTI and NRI) and climate and time-since-deglaciation that also varied through time. Overall, our results suggest that (1) PCS of fossil Angiosperm assemblages during the last 21ka BP have had largely constant spatial patterns, but (2) temporal variability in the relationships between PCS and climate brings into question their usefulness in predictive modeling of community assembly.

Energy landscape analysis elucidates the multistability of ecological communities across environmental gradients

AbstractCompositional multistability is widely observed in multispecies ecological communities. Since differences in community composition often lead to differences in community function, understanding compositional multistability is essential to comprehend the role of biodiversity in maintaining ecosystems. In community assembly studies, it has long been recognized that the order and timing of species migration and extinction influence structure and function of communities. The study of multistability in ecology has focused on the change in dynamical stability across environmental gradients, and was developed mainly for low‐dimensional systems. As a result, methodologies for studying the compositional stability of empirical multispecies communities are not well developed. Here, we show that models previously used in ecology can be analyzed from a new perspective, the energy landscape, to unveil compositional stability in observational data. To show that our method can be applicable to real‐world ecological communities, we simulated assembly dynamics driven by population‐level processes, and show that results were mostly robust to different simulation assumptions. Our method reliably captured the change in the overall compositional stability of multispecies communities over environmental change, and indicated a small fraction of community compositions that may be channels for transitions between stable states. When applied to murine gut microbiota, our method showed the presence of two alternative states whose relationship changes with age, and suggested mechanisms by which aging affects the compositional stability of the murine gut microbiota. Our method provides a practical tool to study the compositional stability of communities in a changing world, and will facilitate empirical studies that integrate the concept of multistability from different fields.