Large extents of intensive land use limit community reorganization during climate warming

Climate change is increasingly altering the composition of ecological communities, in combination with other environmental pressures such as high‐intensity land use. Pressures are expected to interact in their effects, but the extent to which intensive human land use constrains community responses to climate change is currently unclear. A generic indicator of climate change impact, the community temperature index (CTI), has previously been used to suggest that both bird and butterflies are successfully ‘tracking’ climate change. Here, we assessed community changes at over 600 English bird or butterfly monitoring sites over three decades and tested how the surrounding land has influenced these changes. We partitioned community changes into warm‐ and cold‐associated assemblages and found that English bird communities have not reorganized successfully in response to climate change. CTI increases for birds are primarily attributable to the loss of cold‐associated species, whilst for butterflies, warm‐associated species have tended to increase. Importantly, the area of intensively managed land use around monitoring sites appears to influence these community changes, with large extents of intensively managed land limiting ‘adaptive’ community reorganization in response to climate change. Specifically, high‐intensity land use appears to exacerbate declines in cold‐adapted bird and butterfly species, and prevent increases in warm‐associated birds. This has broad implications for managing landscapes to promote climate change adaptation.     

From null community to non-randomly structured actual plant assemblages: parsimony analysis of species co-occurrences

Null community is a spatio‐temporal abstraction of an initial regional species pool from which local species pools and actual community assemblages are organized. Any process that causes joint responses of species with similar susceptibilities affects community assembly. Through time, sequential assembly processes change the composition of a species pool in a way analogous to the one in which evolutionary processes promote character changes from an ancestor to current species. The segregation of species occurrences in an actual community suggests that assembly processes non‐randomly structured the observed community assemblages. However, going backwards to imply the causes of a particular arrangement of species is a non‐trivial challenge. I merge these premises with the philosophical and methodological foundations of cladistics. I propound parsimony analysis of species co‐occurrences as an outstanding means of devising operational hypotheses about the assembly of any non‐randomly structured set of actual community assemblages related to a common species pool. To explore this approach, I used field data gathered in a suite of 10 wetland assemblages. First, I tested independence of 101 plant species occurrences by a null model. As significant non‐random species co‐occurrence was detected, I applied a parsimony analysis taking the species occurrences as attributes, the assemblages as terminal units, and a putative null community constituted by all the present local species as the root of the assembly suite. The analysis produced four most parsimonious trees of assembly relationships. These trees maximize the number of similarities among community assemblages that can be explained by the sole fact of sharing a common regional species pool. One most parsimonious spatio‐temporal arrangement of species occurrence changes was reconstructed on one of the trees. I interpret this reconstruction in terms of assembly events, species exclusions and recruitments, showing the potentialities of this analysis to formulate operational hypotheses about community organization.     

The effect of community on the territorial behavior of the threespot damselfish

Synopsis I examined the hypothesis that animals alter their behavior in response to changes at the community scale of organization, rather than simply reacting to a sequential set of independent interactions with other organisms. The focal species was the threespot damselfish, Stegastes planifrons,a territorial coral reef fish that experiences a high degree of variation in community composition. Field observations of individual threespot damselfish showed a significant increase in the amount of time spent on active territorial defense when the community contained greater proportions of food competitors. Territorial behavior also increased concurrently with higher species diversity in the community. However, no behavioral change was observed in response to the total number of fish entering the defended territory, suggesting that threespot damselfish are responding to more complex environmental cues associated with community structure rather than simple density.     

Scaling environmental change through the community-level: a trait-based response-and-effect framework for plants

Predicting ecosystem responses to global change is a major challenge in ecology. A critical step in that challenge is to understand how changing environmental conditions influence processes across levels of ecological organization. While direct scaling from individual to ecosystem dynamics can lead to robust and mechanistic predictions, new approaches are needed to appropriately translate questions through the community level. Species invasion, loss, and turnover all necessitate this scaling through community processes, but predicting how such changes may influence ecosystem function is notoriously difficult. We suggest that community‐level dynamics can be incorporated into scaling predictions using a trait‐based response–effect framework that differentiates the community response to environmental change (predicted by response traits) and the effect of that change on ecosystem processes (predicted by effect traits). We develop a response‐and‐effect functional framework, concentrating on how the relationships among species' response, effect, and abundance can lead to general predictions concerning the magnitude and direction of the influence of environmental change on function. We then detail several key research directions needed to better scale the effects of environmental change through the community level. These include (1) effect and response trait characterization, (2) linkages between response‐and‐effect traits, (3) the importance of species interactions on trait expression, and (4) incorporation of feedbacks across multiple temporal scales. Increasing rates of extinction and invasion that are modifying communities worldwide make such a research agenda imperative.     

Aridity and chronic anthropogenic disturbance as organizing forces of fruit-feeding butterfly assemblages in a Caatinga dry forest

Anthropogenic disturbances and climate change are expected to reorganize biodiversity on multiple ecological levels from populations to ecosystems, especially in arid and semiarid regions due to environmental filtering imposed by water stress. This paper examines the individual and combined effects of chronic anthropogenic disturbance and increased aridity on the structure of fruit-feeding butterfly assemblages in a human-modified landscape of Caatinga dry forest, in the northeast of Brazil. Butterflies were recorded monthly across old-growth forest stands and their assemblages were described in terms of taxonomic and functional community-level attributes confronted to different levels of chronic disturbance and aridity. Butterfly assemblages were species-poor but had high species replacement (turnover) along both the chronic disturbance and aridity gradients. We observed a negative effect of aridity on alpha and beta diversity of butterfly assemblages. Butterfly assemblages across forest stands exposed to high levels of chronic disturbance and aridity had a nested structure. Functional diversity (Rao's Q) and the community-weighted means (CWM) of ocellus-bearing species and monocot-feeding larvae were negatively and positively affected by increased aridity and chronic disturbance, respectively. Our findings suggest that aridity and its combination with chronic disturbance have a drastic effect on the structure of butterfly assemblages in the Caatinga dry forest. These findings highlight that rainfall and chronic disturbances as major drivers of biological reorganization in human-modified landscapes. As aridity increases, Caatinga tends to support taxonomically and functionally impoverished and highly distorted assemblages. Abstract in Portuguese is available with online material     

Linking community and disease ecology: the impact of biodiversity on pathogen transmission

The increasing number of zoonotic diseases spilling over from a range of wild animal species represents a particular concern for public health, especially in light of the current dramatic trend of biodiversity loss. To understand the ecology of these multi-host pathogens and their response to environmental degradation and species extinctions, it is necessary to develop a theoretical framework that takes into account realistic community assemblages. Here, we present a multi-host species epidemiological model that includes empirically determined patterns of diversity and composition derived from community ecology studies. We use this framework to study the interaction between wildlife diversity and directly transmitted pathogen dynamics. First, we demonstrate that variability in community composition does not affect significantly the intensity of pathogen transmission. We also show that the consequences of community diversity can differentially impact the prevalence of pathogens and the number of infectious individuals. Finally, we show that ecological interactions among host species have a weaker influence on pathogen circulation than inter-species transmission rates. We conclude that integration of a community perspective to study wildlife pathogens is crucial, especially in the context of understanding and predicting infectious disease emergence events.     

Waders in winter: long-term changes of migratory bird assemblages facing climate change

Effects of climate change on species occupying distinct areas during their life cycle are still unclear. Moreover, although effects of climate change have widely been studied at the species level, less is known about community responses. Here, we test whether and how the composition of wader (Charadrii) assemblages, breeding in high latitude and wintering from Europe to Africa, is affected by climate change over 33 years. We calculated the temporal trend in the community temperature index (CTI), which measures the balance between cold and hot dwellers present in species assemblages. We found a steep increase in the CTI, which reflects a profound change in assemblage composition in response to recent climate change. This study provides, to our knowledge, the first evidence of a strong community response of migratory species to climate change in their wintering areas.     

Large-scale changes in community composition: determining land use and climate change signals

Human land use and climate change are regarded as the main driving forces of present-day and future species extinction. They may potentially lead to a profound reorganisation of the composition and structure of natural communities throughout the world. However, studies that explicitly investigate both forms of impact--land use and climate change--are uncommon. Here, we quantify community change of Dutch breeding bird communities over the past 25 years using time lag analysis. We evaluate the chronological sequence of the community temperature index (CTI) which reflects community response to temperature increase (increasing CTI indicates an increase in relative abundance of more southerly species), and the temporal trend of the community specialisation index (CSI) which reflects community response to land use change (declining CSI indicates an increase of generalist species). We show that the breeding bird fauna underwent distinct directional change accompanied by significant changes both in CTI and CSI which suggests a causal connection between climate and land use change and bird community change. The assemblages of particular breeding habitats neither changed at the same speed and nor were they equally affected by climate versus land use changes. In the rapidly changing farmland community, CTI and CSI both declined slightly. In contrast, CTI increased in the more slowly changing forest and heath communities, while CSI remained stable. Coastal assemblages experienced both an increase in CTI and a decline in CSI. Wetland birds experienced the fastest community change of all breeding habitat assemblages but neither CTI nor CSI showed a significant trend. Overall, our results suggest that the interaction between climate and land use changes differs between habitats, and that comparing trends in CSI and CTI may be useful in tracking the impact of each determinant.     

Resources Alter the Structure and Increase Stochasticity in Bromeliad Microfauna Communities

Although stochastic and deterministic processes have been found to jointly shape structure of natural communities, the relative importance of both forces may vary across different environmental conditions and across levels of biological organization. We tested the effects of abiotic environmental conditions, altered trophic interactions and dispersal limitation on the structure of aquatic microfauna communities in Costa Rican tank bromeliads. Our approach combined natural gradients in environmental conditions with experimental manipulations of bottom-up interactions (resources), top-down interactions (predators) and dispersal at two spatial scales in the field. We found that resource addition strongly increased the abundance and reduced the richness of microfauna communities. Community composition shifted in a predictable way towards assemblages dominated by flagellates and ciliates but with lower abundance and richness of algae and amoebae. While all functional groups responded strongly and predictably to resource addition, similarity among communities at the species level decreased, suggesting a role of stochasticity in species-level assembly processes. Dispersal limitation did not affect the communities. Since our design excluded potential priority effects we can attribute the differences in community similarity to increased demographic stochasticity of resource-enriched communities related to erratic changes in population sizes of some species. In contrast to resources, predators and environmental conditions had negligible effects on community structure. Our results demonstrate that bromeliad microfauna communities are strongly controlled by bottom-up forces. They further suggest that the relative importance of stochasticity may change with productivity and with the organizational level at which communities are examined.     

Long-term changes in temperate marine fish assemblages are driven by a small subset of species

The species composition of plant and animal assemblages across the globe has changed substantially over the past century. How do the dynamics of individual species cause this change? We classified species into seven unique categories of temporal dynamics based on the ordered sequence of presences and absences that each species contributes to an assemblage time series. We applied this framework to 14,434 species trajectories comprising 280 assemblages of temperate marine fishes surveyed annually for 20 or more years. Although 90% of the assemblages diverged in species composition from the baseline year, this compositional change was largely driven by only 8% of the species' trajectories. Quantifying the reorganization of assemblages based on species shared temporal dynamics should facilitate the task of monitoring and restoring biodiversity. We suggest ways in which our framework could provide informative measures of compositional change, as well as leverage future research on pattern and process in ecological systems.     

Immigration and zooplankton community responses to nutrient enrichment: a mesocosm experiment

Dispersal can be an important determinant of local diversity and species composition, but evidence for effects of the regional species pool on local zooplankton communities has been mixed. Theory and experiments suggest that immigration will be necessary for maintenance of community diversity and functioning during periods of environmental change; conversely, fluctuating resource levels may increase the likelihood of invasion success. We conducted a factorial-design mesocosm experiment to test the effects of a nutrient pulse and weekly immigration from other lakes on the diversity and composition of a pelagic zooplankton community. Contrary to expectations, there were no interactive effects of nutrient enrichment and immigration on any measure of diversity, and the initial shift in community composition in response to the nutrient pulse did not depend on the introduction of new species or genotypes from more productive lakes. Although immigration increased species richness in enclosures, success of most colonising species was poor. However, the dispersal treatment appears to have enabled a stronger predator response to increased herbivore numbers in nutrient-pulsed enclosures, leading to an eventual decline in the abundance of some herbivorous species in response to immigration. We conclude that community invasibility was not influenced by productivity, and that dispersal limitation did not strongly constrain the response of the zooplankton community to our applied disturbance. This indicates an unexpected resistance to change in species composition and diversity in spite of disturbance, and suggests that, in our study system, changes in the abundance of resident species are more important than introductions of new species in the community response to short-term environmental change.Electronic Supplementary Material Supplementary material is available to authorized users in the online version of this article at .     

Functional reorganization and productivity of a water-limited annual plant community

Plant Ecology - Changes in plant community structure in response to environmental change can be defined as community reorganization. In water-limited regions, the size of annual plants is related...     

Assessing impacts of ecosystem engineers on community organization: a general approach illustrated by effects of a high-Andean cushion plant

Comparative and integrative tools are of fundamental value in ecology for understanding outcomes of biological processes, and making generalizations and predictions. Although ecosystem engineering has been shown to play a fundamental role in community organization, there are no standardized methods to measure such effects. We present a framework and methodology for assessing the impact of physical ecosystem engineers on three general features of community organization: (1) species richness and composition, (2) stability of richness over time, and (3) dominance patterns of species assemblages. We then apply the framework and methodology to assess the effects of the cushion plant Azorella monantha on high-Andean plant communities on two mountaintops. Substrate temperatures, soil moisture and the availability of mineral nutrient resources were compared between A. monantha and surrounding open areas to ascertain whether cushions altered abiotic environmental conditions, while community analysis assessed changes in species richness, composition and abundances at patch and landscape levels. Cushions thermally buffered temperature extremes and increased soil moisture, but had no detectable effect on soil mineral nutrients. Cushion habitat was not more species rich than surrounding areas, but cushions added new species into the community, altering species composition and markedly enhancing landscape-level richness. Cushions also showed potential for stabilizing species richness over time, and changed patterns of species dominance. Findings were consistent across mountaintops. We evaluate the general utility of the framework and call for its application in other systems as a means to generate comparative data sets for assessing the general effects of ecosystem engineers on community organization.     

Reconciling neutral community models and environmental filtering: theory and an empirical test

It is widely believed that the neutral theory of biodiversity cannot be used for parameter inference if the assumption of neutrality is not met. The goal of this work is to extend this neutral framework to quantify the intensity of recruitment limitation (limited dispersal plus environmental filtering) in natural species assemblages. We model several local communities as part of a larger metacommunity, and we assume that neutrality holds in each local community, but not in the metacommunity. The immigration rate m does not only reflect dispersal limitation into a given local community, but also the intensity of environmental filtering. We develop a novel statistical method to infer the immigration parameter m in each local community. Using simulated datasets, we show that m indeed depends on both dispersal limitation and on the intensity of environmental filtering. We then apply this method to a network of tropical tree plots in central Panama. Inferred recruitment rates m were positively correlated with the fraction of trees dispersed by mammals, and with annual rainfall, possibly due to a weaker environmental filtering as rainfall increases. Finally, m, as estimated from trees greater than 1 cm trunk diameter, were significantly larger than an estimation based on trees greater than 10 cm trunk diameter. This suggests a cumulative effect of environmental filtering upon trees throughout their ontogeny.     

A novel approach to assess livestock management effects on biodiversity of drylands

In drylands livestock grazing is the main production activity, but overgrazing due to mismanagement is a major cause of biodiversity loss. Continuous grazing around water sources generates a radial gradient of grazing intensity called the piosphere. The ecological sustainability of this system is questionable and alternative management needs to be evaluated. We apply simple indicators of species response to grazing gradients, and we propose a novel methodological approach to compare community response to grazing gradients (double reciprocal analysis). We assessed degradation gradients of biodiversity under different management strategies in semiarid rangelands of the Monte desert (Argentina) by analyzing changes in vegetation, ants and small mammal richness and diversity, and variation due to seasonality. At the species level, we determined the trend in abundance of each species along the gradient, and the potential cross-taxa surrogacy. At the community level, the new methodological consists of assessing the magnitude of biodiversity degradation along different piospheres by comparing the slopes of linear functions obtained by the double reciprocal analysis. We found that most species showed a decreasing trend along the gradient under continuous grazing; while under rotational grazing fewer species showed a decreasing trend, and a neutral trend (no change in the abundance along the gradient of grazing intensity) was the most common. We found that vegetation cannot be used as a surrogacy taxon of animal response. Moreover, weak cross-taxa surrogacy was found only for animal assemblages during the wet season. The double reciprocal analysis allowed for comparison of multi-taxa response under different seasons and management types. By its application, we found that constrains in precipitation interacted with disturbance by increasing the negative effect of grazing on vegetation, but not on animal assemblages. Continuous grazing causes biodiversity loss in all situations. Rotational grazing prevents the occurrence of vegetation degradation and maintains higher levels of animal diversity, acting as an opportunity for biodiversity conservation under current scenarios of land use extensification. Our approach highlights the importance of considering multi-taxa and intrinsic variability in the analysis, and should be of value to managers concerned with biodiversity conservation.     

Environmental filtering and spatial effects on metacommunity organisation differ among littoral macroinvertebrate groups deconstructed by biological traits

We examined spatial and environmental effects on the deconstructed assemblages of littoral macroinvertebrates within a large lake. We deconstructed assemblages by three biological trait groups: body size, dispersal mode and oviposition behaviour. We expected that spatial effects on assemblage structuring decrease and environmental effects increase with increasing body size. We also expected stronger environmental filtering and weaker spatial effect on the assemblages of flying species compared with assemblages of non-flying species. Stronger effect of environmental filtering was expected on the assemblages with species attaching eggs compared with assemblages of species with free eggs. We used redundancy analysis with variation partitioning to examine spatial and environmental effects on the deconstructed assemblages. As expected, the importance of environmental filtering increased and that of spatial effects decreased with increasing body size. Opposite to our expectations, assemblages of non-flying species were more affected by environmental conditions compared to assemblages of flying species. Concurring with our expectations, the importance of environmental filtering was higher in structuring assemblages of species attaching eggs than in structuring those with freely laid eggs. The amount of unexplained variation was higher for assemblages with small-sized to medium-sized species, flying species and species with free eggs than those with large-sized species, non-flying species and species with attached eggs. Our observations of decreasing spatial and increasing environmental effects with increasing body size of assemblages deviated from the results of previous studies. These results suggest differing metacommunity dynamics between within-lake and among-lake levels and between studies covering contrasting taxonomic groups and body size ranges.     

Phylogenetic and morphological relationships between nonvolant small mammals reveal assembly processes at different spatial scales

The relative roles of historical processes, environmental filtering, and ecological interactions in the organization of species assemblages vary depending on the spatial scale. We evaluated the phylogenetic and morphological relationships between species and individuals (i.e., inter‐ and intraspecific variability) of Neotropical nonvolant small mammals coexisting in grassland‐forest ecotones, in landscapes and in regions, that is, three different scales. We used a phylogenetic tree to infer evolutionary relationships, and morphological traits as indicators of performance and niche similarities between species and individuals. Subsequently, we applied phylogenetic and morphologic indexes of diversity and distance between species to evaluate small mammal assemblage structures on the three scales. The results indicated a repulsion pattern near forest edges, showing that phylogenetically similar species coexisted less often than expected by chance. The strategies for niche differentiation might explain the phylogenetic repulsion observed at the edge. Phylogenetic and morphological clustering in the grassland and at the forest interior indicated the coexistence of closely related and ecologically similar species and individuals. Coexistence patterns were similar whether species‐trait values or individual values were used. At the landscape and regional scales, assemblages showed a predominant pattern of phylogenetic and morphological clustering. Environmental filters influenced the coexistence patterns at three scales, showing the importance of phylogenetically conserved ecological tolerances in enabling taxa co‐occurrence. Evidence of phylogenetic repulsion in one region indicated that other processes beyond environmental filtering are important for community assembly at broad scales. Finally, ecological interactions and environmental filtering seemed important at the local scale, while environmental filtering and historical colonization seemed important for community assembly at broader scales.     

Biologic interactions determining geographic range size: a one species response to phylogenetic community structure

Range size variation in closely related species suggests different responses to biotic and abiotic heterogeneity across large geographic regions. Species turnover generates a wide spectrum of species assemblages, resulting in different competition intensities among taxa, creating restrictions as important as environmental constraints. We chose to adopt the widely used phylogenetic relatedness (NRI) measurement to define a metric that depicts competition strength (via phylogenetic similarity), which one focal species confronts in its environment. This new approach (NRI_focal) measures the potential of the community structure effect over performance of a single species. We chose two ecologically similar Peucaea sparrows, which co‐occur and have highly dissimilar range size to test whether the population response to competition intensity is different between species. We analyzed the correlation between both Peucaea species population sizes and NRI_focal using data from point counts. Results indicated that the widespread species population size was not associated with NRI_focal, whereas the population of restricted‐sized species exhibited a negative relationship with competition intensity. Consequently, a species' sensitivity to competition might be a limiting factor to range expansion, which provides new insights into geographic range analysis and community ecology.     

Response of macroalgal assemblages from rockpools to climate change: effects of persistent increase in temperature and CO2

Anthropogenically induced global climate change has important implications for marine ecosystems with unprecedented ecological and economic consequences. Climate change will include the simultaneous increase of temperature and CO₂ concentration in oceans. However, experimental manipulations of these factors at the community scale are rare. In this study, we used an experimental approach in mesocosms to analyse the combined effects of elevated CO₂ and temperature on macroalgal assemblages from intertidal rock pools. Our model systems were synthetic assemblages of varying diversity and understory component and canopy species identity. We used assemblages invaded by the non‐indigenous canopy forming alga Sargassum muticum and assemblages with the native canopy species Cystoseira tamariscifolia. We examined the effects of both climate change factors on several ecosystem functioning variables (i.e. photosynthetic efficiency, productivity, respiration and biomass) and how these effects could be shaped by the diversity and species identity of assemblages. CO₂ alone or in combination with temperature affected the performance of macroalgae at both individual and assemblage level. In particular, high CO₂ and high temperature (20°C) drastically reduced the biomass of macroalgal assemblages and affected their productivity and respiration rates. The identity of canopy species also played an important role in shaping assemblage responses, whereas species richness did not seem to affect such responses. Species belonging to the same functional effect group responded differently to the same environmental conditions. Data suggested that assemblages invaded with S. muticum might be more resistant in a future scenario of climate change. Thus, in a future scenario of increasing temperature and CO₂ concentration, macroalgal assemblages invaded with canopy‐forming species sharing response traits similar to those of S. muticum could be favoured.     

Community assembly rules affect the diversity of expanding communities

Despite centuries of interest in species range limits, few studies have taken a whole community into consideration. Actually, multiple species may simultaneously respond to environmental changes, for example, global warming, leading a series of dynamical communities toward the advancing front. We investigated multiple species range expansions through the analysis of a two‐species dispersion model and simulations of multiple species assemblages regulated by neutral and fecundity–survival trade‐offs (FSTs), respectively, and found that species assemblages regulated by different mechanisms would initiate different expanding patterns in geographic ranges in response to environmental changes. The neutral model generally predicts a higher biodiversity near the core of an expanding range, and a lower community similarity compared with a FST model. Without considering the evolution of life history traits, an assortment of the reproduction ability happens at the advancing front under FSTs at the expense of a higher death rate or lower competitive ability. These results emphasize the importance of community assembly rules to the biodiversity maintenance of range expanding communities.